Co-signers & guarantors on DIY landlord software — screening, signing, notices, mid-lease adds

• Is: a side-by-side of how RentRedi, TurboTenant, and Avail handle a third party who backs a lease. It covers application and screening (and who pays), how the tool records them (tenant, co-signer, or additional signer), the signing path, whether they get portal access or charge notices, adding one mid-lease, and free vs paid gates. It also has a decision table, a worked student-plus-parent example with the ways it goes wrong, a checklist, and an FAQ.
• Is not: a guaranty form, or advice on whether your guaranty is enforceable, what income you may require of a guarantor, or how to collect from one. The legal orientation below comes from attorney-written plain-English sources and two state examples (Colorado and California) and is only a starting point.
• Not the same as: adding a roommate who will live there. That person is a co-tenant (see roommate & co-tenant changes). It’s also not a third-party guarantor company. Avail’s education mentions these as an alternative, but we didn’t review any.
• Uncertainty rule: “co-signer” and “guarantor” are used inconsistently by all three vendors and by legal publishers (details below). The words in your signed document matter more than the label in the app. Avail’s support article “Add a co-applicant to your rental application” exists but rendered as an empty JS shell for us, so the Avail rows rely on education pages (2025–2026) and community posts (Dec 2021, Mar 2026).

• Co-signer (as most vendor education uses it): signs the lease and is liable from day one. Avail’s Lease Guarantor vs. Co-Signer guide (updated Jun 4, 2026) says a co-signer “shares equal, immediate responsibility” and “typically hold[s] occupancy rights.” RentRedi’s When to Require a Lease Guarantor says co-signers and co-tenants “have the same duty as the primary tenant to pay rent.”
• Guarantor (as most vendor education uses it): a financial backstop who usually doesn’t live there. RentRedi: “A landlord cannot attempt to collect rent from a lease guarantor until after a tenant has defaulted.” Avail: liability is “contingent upon default,” and landlords “may be legally required to exhaust” remedies against the tenant first, so the agreement should define “notice requirements, cure periods, and the exact default events.”
• But the words aren’t used consistently. Lawyers.com’s Should Landlords Require Cosigners? (Jul 28, 2026) describes a cosigner as “jointly and severally liable with the tenant,” so you can pursue “the tenant, the cosigner, or both,” and Nolo sells its Residential Lease Cosigner Agreement for a “cosigner (also known as a lease guarantor).” TurboTenant’s co-signer article says a co-signer “may choose to live there,” while its application FAQ says a co-signer “is not necessarily a tenant.” Write the role into the document: primary or secondary liability, whether the person can occupy the unit, and what triggers payment.
• Joint and several vs limited: a joint-and-several guaranty or co-signer clause backs everything owed under the lease. A limited guaranty narrows it, for example to a dollar or months-of-rent cap, to one roommate’s share, or to the initial term only. Limits are a drafting choice for your counsel. No tool here enforces them, and the ledger will still show the full charge.
• The guaranty must actually be signed, and it must reference the lease. Nolo’s Janet Portman, answering a parent who signed only the application: the guarantor “must sign either the lease itself or a guarantee agreement that references the lease,” and a promise to guarantee a lease the person hasn’t seen isn’t one a court is likely to enforce (AAOA reprint). Screening someone doesn’t make them a guarantor.
• Renewals and amendments: Lawyers.com advises having the cosigner sign any amendments. TurboTenant’s co-signer article says the co-signer’s responsibility extends through “extensions, renewals, amendments, or updates,” but that describes its agreement language. Your own form may say something else.
• “No cosigners” policies and disability: Lawyers.com says a no-cosigner policy is legal with one exception. If an applicant with a disability whose income is inadequate (but who is otherwise suitable) asks you to accept a solvent, stable cosigner, “federal law requires you to make an accommodation.”
• Income caps and source of income (state examples only): Colorado C.R.S. 38-12-904(1)(d) says a landlord “shall not require a prospective tenant to have an annual amount of income that exceeds two hundred percent of the annual cost of rent.” For a subsidized applicant, the 200% applies only to the tenant’s portion, and credit scores can’t be considered (1)(c). California’s CRD source-of-income FAQ says an income standard for voucher holders may consider “only… the tenant’s portion of the rent,” and that all lawful, verifiable income must be counted. Neither text mentions guarantors. We couldn’t confirm whether Colorado’s 200% cap also limits what you may require of a guarantor, or whether requiring a guarantor because a voucher holder fails a total-rent income test is lawful (it plainly conflicts with the spirit of both). Ask counsel before you set guarantor criteria.
• Colorado screening-fee wrinkle: 38-12-904(1.5) requires most landlords to accept a portable tenant screening report (30 days old or less) and bars charging an application fee to someone who provides one, unless you meet the one-fee-at-a-time / 20-day refund exemption. Whether a guarantor counts as a “prospective tenant” here isn’t stated. The safe operating assumption is to treat them the same.

• Screen: if the guarantor applied, use Applications → Screening → Request Screening. If not, add them to the unit with invite Skip/Later → ⋮ Screen Tenant (uncheck Income & Asset Verification only if you don’t need it, though for a guarantor you usually do).
• Sign: Tenants → tenant → Documents → Upload File → Signature Request → upload the lease and guaranty (or one combined PDF) → select the tenant and the guarantor. Every requested signer must sign before you can countersign.
• Charges: decide whether the guarantor goes on the rent charge. On it means they can see the shared charges every month, so they’re effectively watching. Off it means a quieter relationship, but you have to send the default notice yourself.
• Autopay: tenant-set amount (see late fees & autopay). A guarantor on the charge could set autopay too, which is rarely what anyone intends, so say so in writing.
• Labeling: the Tenants list will show the guarantor as a tenant. Note “GUARANTOR — non-occupant” in their profile and in your rent roll so headcounts and occupancy stay right.

• Apply: the co-signer chooses “co-signer” at the start of their own application (unique email) and pays their own fee: $55, or $45 on Essentials/Pro. If they chose the wrong role, switch it between Tenant and Co-Signer after submission. An invited co-signer won’t appear until they submit.
• Accept: decisions are per person. Accepting the tenant doesn’t accept the co-signer, and vice versa.
• Lease: Lease Profile → Get a [state] Lease Agreement → People on the Lease → Tenants: the tenant only → “Are there any co-signers?” Yes → name + email → TT co-signer agreement (or your own form with fields placed) → send. Sending requires a paid tier.
• Portal (optional): to let the co-signer see or pay charges, add them to the lease profile’s tenant section and invite them. Without that, they get no portal access. For a non-occupant guarantor, that’s often the right call, but you have to send the default notice yourself.
• Mid-lease: no addendum path. You need a new lease agreement that includes the co-signer. Existing co-signers are auto-added as signers on later addendums, which is a good sign that TT keeps them in the paper trail.

• Apply: the tenant adds the guarantor as a co-applicant, or you invite the guarantor separately and choose fewer reports (e.g., credit only), per the 2021 staff post. Cost varies by state and depends on the reports you pick.
• Lease: staff advice is to have both sign as “lessee” and add a clause stating the guarantor won’t occupy. Our caution: a guarantor who signs as a lessee may be treated as a co-tenant. If you want true secondary liability, have counsel draft a separate guaranty and attach it (or sign it offline and upload it), and reference it in the lease.
• Existing lease: add the guarantor as a payer + free amendment, signed offline by every original signer, then upload.
• Notices: once they’re on the payment list, assume they see what any payer sees. Confirm with support, because no readable doc covers it.
• Plus: custom application questions let you ask “applying as tenant or guarantor?” up front.

• Screened, never signed: P passed screening, but the guaranty was never sent or the signature request was never completed. Collectible from P under a guaranty: $0 (the Portman point).
• Signed, never told: P co-signed on TurboTenant but was never added to the portal, and nobody wrote to P until June. The guaranty may still be good, but P is now facing $5,550 instead of a $1,850 phone call in March, and a guaranty that requires prompt notice may be weakened. Put a written default notice to the guarantor in your late-rent routine.
• Guarantor turned co-tenant: P signed the Avail lease as a “lessee” with a one-line clause. When the lease is enforced, P argues they’re a co-tenant with a right to stay, or S argues P’s presence is permitted. Avoidable with counsel’s separate guaranty or a clear occupancy clause.
• Guarantor autopay by accident: on RentRedi, P was put on the rent charge and set autopay “to help.” S pays too, and the ledger shows $3,700 collected in a $1,850 month. Now you’re refunding or crediting (partial payments & credits).
• Renewal without the guarantor: S renews for 2028 at $1,925 and only S signs. Whether P’s guaranty reaches the new term depends on its wording (TT’s co-signer language claims renewals, while your own form may not). Re-sign or reaffirm at renewal.
• Mid-lease rescue that doesn’t fit TT: in June you ask for a guarantor. TT can’t add a new co-signer by addendum, so you need a whole new lease. On RR and Avail you can paper it, but ask counsel whether a guaranty signed after move-in needs something given in exchange to be enforceable in your state.
• Handoff: if it goes to counsel, they’ll want the signed guaranty, the screening authorization, every notice to P, and the ledger (eviction & collections handoff).

1. Write your criteria first: when you accept a guarantor, what income, credit, and history you require of one, and whether you accept co-signers at all. Apply them to everyone (applications).
2. Check your state: income caps (CO 200%), source-of-income rules (tenant-portion tests), application-fee and portable-report rules, deposit caps, and the disability-accommodation exception.
3. Decide the role: co-signer (primary, joint and several), guarantor (secondary, after default), or limited guaranty. Decide whether they may occupy.
4. Separate application + screening for the guarantor, with their own email and their own fee (screening costs). TT: role = Co-Signer. Avail: co-applicant or a separate invite.
5. Accept each person separately (TT decisions are per person) and keep the screening authorization.
6. Get the guaranty signed, and make sure it names the lease (address, dates, rent). TT co-signer field + agreement, RR Signature Request, or Avail attachment/offline (lease & e-sign).
7. Confirm every signature is complete before keys. A pending request isn’t a guaranty.
8. Decide portal vs no portal for the guarantor, and make sure they can’t autopay by accident.
9. Label them as a non-occupant guarantor in profiles, the rent roll, and the occupancy count.
10. Store the guaranty with the lease (document vault).
11. Add a default-notice step to your late-rent routine: on the day you’d send a past-due notice, also write to the guarantor (notices).
12. Re-paper at renewal, amendment, or tenant change. Have the guarantor sign or reaffirm (renewals, roommate changes).
13. Mid-lease add: TT means a new lease. RR means screen, then Signature Request. Avail means payer + amendment signed offline by all.
14. When switching tools, export the signed guaranty, since the new tool won’t carry a “co-signer” label (switch checklist).

Does the guarantor have to pay their own screening fee?

By default, yes, in all three tools: RR $39.99 / $49.99, TT $55 or $45 on paid tiers, Avail varies by state. TT and Avail let the landlord pay instead. In Colorado, a guarantor who provides a recent portable screening report may not be chargeable, so confirm with counsel.

Can I screen a guarantor for credit only?

Avail staff say some landlords do, by inviting the guarantor separately and picking fewer reports. RR and TT bundle credit, criminal, and eviction checks in their standard requests. Whatever you choose, use it for every guarantor.

Will the guarantor get late-rent reminders automatically?

Only if you make them a tenant or payer on the charge (RR shared charge, TT tenant section + portal invite, Avail payer). None of the three has a “notify the guarantor only on default” setting that we found. Most landlords should send that notice themselves.

Can I add a co-signer after the lease is signed?

TurboTenant: not with an addendum. You need a new lease agreement. RentRedi: upload a guaranty and send a Signature Request. Avail: add them as a payer and sign an amendment offline. Whether a guaranty signed mid-lease is enforceable is a state contract-law question.

Is a co-signer the same as a guarantor?

Vendors usually say no (co-signer means immediate liability and maybe occupancy, guarantor means after default and no occupancy), but legal publishers often use “cosigner” for both. Your signed document decides.

Can I refuse all co-signers?

Lawyers.com says a no-cosigner policy is generally legal, except that you must consider a solvent cosigner offered as an accommodation by an applicant with a disability. Source-of-income rules can also change how you apply income tests.

Should the guarantor sign the lease or a separate guaranty?

Either can work if it references the lease (Portman). TT attaches its co-signer agreement to the lease. Avail’s staff route has the guarantor sign as a lessee, which is simpler but blurs roles. A separate guaranty drafted by counsel is the clearest way to get secondary or limited liability.

• Want a real co-signer role from application to signature: TurboTenant (role at application, lease-builder co-signer field + agreement). Budget for a paid tier to send it, and plan your own default notices.
• Bring-your-own-guaranty landlords: RentRedi’s Signature Request with ID + selfie verification, and Screen Tenant for a guarantor who didn’t apply. One flat plan.
• Free-first: Avail’s free application, screening, and lease, with the guarantor as co-applicant. Get the guaranty wording right outside the app.
• Student rentals with parents on every lease: standardize one guaranty form and one default-notice letter, and log the guarantor’s contact info with each lease. The tool won’t remember for you.

• TurboTenant: its co-signer article says a co-signer “may choose to live there,” while its application FAQ says a co-signer “is not necessarily a tenant.” The co-signer agreement is described both as auto-attached in the lease builder (Aug 2025 announcement) and as part of the Forms Pack “included with Premium,” while pricing lists the Forms Pack at $199. Plan names (Essentials / Pro / Premium) don’t appear on the pricing page, which shows $12.42 and $16.48/mo tiers.
• RentRedi: a Feb 2026 blog FAQ describes applicants adding guarantor contact details or “requesting a guarantor link.” The help center describes only separate accounts and applications, so treat the link as unconfirmed. We found nothing on whether a guarantor off the rent charge receives any reminders.
• Avail: no guarantor role. The key staff answers are community posts (Dec 2021, Mar 2026), and the co-applicant support article didn’t render. Plus pricing wasn’t shown. Whether adding a guaranty clause needs Plus customization is unclear.
• Law: Colorado’s 200% income cap and portable-report rules speak of the “prospective tenant.” We couldn’t confirm how they apply to guarantors. Source-of-income rules in CA and CO make total-rent income tests for voucher holders risky. Other states differ.