How do co-signers and lease guarantors work?
A co-signer or guarantor is someone who agrees to pay if the tenant does not. A co-signer usually signs the lease itself and shares responsibility for it, while a guarantor signs a separate guaranty promising to pay the tenant's debts under the lease. Either way the promise should be in writing, and if a screening report led you to require one, the FTC says you owe the applicant an adverse action notice.
Co-signer and guarantor: the difference
The words are used loosely, and your documents decide what each person owes. The usual pattern:
| Co-signer | Guarantor | |
|---|---|---|
| What they sign | The lease, as a party | A separate guaranty |
| Lives in the unit? | No, in most setups | No |
| When they owe | Shares the lease obligations | When the tenant defaults |
| Rights to the unit | Depends on the lease; often written to have none | None |
| Common for | Students, first-time renters | Students, thin credit, high rent-to-income |
New York shows why paper matters. Its General Obligations Law says a special promise to answer for the debt or default of another person is void unless it is in writing and signed by the person making it (GOL 5-701). Many states have a similar rule. Never rely on a phone call or a verbal yes.
When to ask for one
Ask for a guarantor as a written, standard alternative when an applicant falls short on one criterion, not as an extra hurdle for some people. Common triggers in written criteria:
- Income below your multiple, for example under three times rent (see the 3x rent rule).
- No rental or credit history, such as a first apartment.
- A credit or rental record that fails your written standard.
If a consumer report played any part, the requirement is an adverse action. The FTC lists requiring a co-signer on the lease as an example, so send the notice even though you are approving the applicant.
Qualifying the guarantor
A guarantor who cannot pay is no protection. Screen them like an applicant, with their written consent, and use a higher bar since they also carry their own housing costs.
- Get a signed application and consent to obtain reports from the guarantor.
- Verify income, often four to five times the monthly rent in written criteria.
- Check identity and contact details; a guarantor you cannot reach later is not useful.
- Decide whether out-of-state guarantors are accepted, and say so in your criteria.
- Have them sign the guaranty at the same time as the lease, with a copy of the lease attached.
Example a made-up applicant earns $3,600 a month for a $1,500 unit. The owner requires three times rent, or $4,500, so she is $900 short. The written criteria allow a guarantor earning five times rent, $7,500 a month. Her father earns $8,200 a month, passes the check and signs. Seven months later she misses $1,500 of rent; after the notice the guaranty requires, he pays it and the account is current.
What the guaranty should say
- Which lease, unit and tenants it covers, with the lease attached.
- What it covers: rent, fees, damage, legal costs where allowed.
- Whether it covers renewals and rent increases, or only the first term. Say it plainly, because a guarantor may argue a later change was not agreed.
- A dollar cap, if you offer one, or "all amounts due under the lease".
- How you will notify the guarantor of a default, and to which address.
- Signature, date and, if your state or lender expects it, notarization.
Keep the guarantor informed about material changes. In New York, a tenant asking to sublet must include the written consent of any guarantor (Real Property Law 226-b), a sign of how closely the guarantor is tied to the lease.
How DoorKeeping handles it
DoorKeeping keeps each tenant's ledger by property, so a late balance is clear to the dollar when you need to contact a guarantor. The signed lease is kept with the property's documents, so the guaranty terms are easy to find. Any notice that involves money or a legal step waits for your one-tap approval. DoorKeeping is $2 per unit per month and gives no legal advice.
Sources
- FTC, Using Consumer Reports: What Landlords Need to Know, read Oct 29, 2026
- New York General Obligations Law 5-701, read Oct 29, 2026
- New York Real Property Law 226-b, read Oct 29, 2026
Questions
- Is a co-signer responsible if the tenant breaks the lease?
- Usually yes, for what the lease or guaranty covers, such as unpaid rent and damage. The exact reach depends on the documents they signed.
- Does requiring a co-signer need an adverse action notice?
- Yes, if a consumer report played any part in the decision. The FTC lists requiring a co-signer as an adverse action.
- Can a guarantor live in the apartment?
- A guarantor is normally not an occupant. Anyone who will live there should be on the lease as a tenant or listed occupant.