My dad has agreed to cosign a lease with me but I am afraid my application will just be thrown out since I cannot provide a credit score or any proof of income. Learn the essential steps on how to add a cosigner to a lease to strengthen your rental agreement.This publication describes what the law requires of both landlords and tenants and also describes some terms that are in typical leases. A cosigner for an apartment takes on the financial responsibility for a lease. Learn how having a cosigner can help someone get approved for an apartment. This guide will provide all the necessary information you need to screen, process, and add a cosigner to a lease. Adding a cosigner is pretty straightforward with these steps: Do your research: Treat the apartment cosigner as an additional tenant. A cosigner is a person who signs a lease together with the renter and, as a consequence, makes a legal promise to pay the rent if the renter fails to do so. Read the application before you fill it out.