Learn the essential steps on how to add a cosigner to a lease to strengthen your rental agreement. Any "ground rules" are totally unenforceable.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. Signer is a thirdparty person who signs a lease agreement along with the applicant, but they generally won't live on the property. As a co-signer, you don't have to live in the apartment but your name will be on the lease and you'll be legally obligated to follow the terms of the lease. Adding a cosigner is pretty straightforward with these steps: Do your research: Treat the apartment cosigner as an additional tenant. This guide will provide all the necessary information you need to screen, process, and add a cosigner to a lease. Complete the Co-Signer Guarantor form, sign the form and have it NOTARIZED. 2. Complete the Co-Signer Credit Application form with your information. 3. If the landlord is not convinced that you will be able to make your payments, he or she may require you to get a cosigner.