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. 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.A cosigner for a rental property is someone who agrees to pay the rent if you cannot. Learn the essential steps on how to add a cosigner to a lease to strengthen your rental agreement. 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. Guarantors must have an individual gross monthly income that is equal to or greater than 4x the monthly rent. A guarantor or cosigner is someone who signs the lease with you and is legally required to pay your rent if you fail to do so. We have student's sign the lease then we have parent's sign a guarantor form that says they will be responsible for paying the rent. Dad would have to qualify just as son if he's on the lease as tenant.. cosigner just financial.