Is there any way I can indicate on my application that I will be using a cosigner? If you'd like your applicant to have a cosigner or guarantor, you should have them fill out an application, too.2. Co-signer Applications: Co-signers must also fill this form if they are financially responsible for the lease. When requested, applicants can enter other co-applicants, co-signers, and guarantors they'll be applying with on their rental application. This guide will provide all the necessary information you need to screen, process, and add a cosigner to a lease. Find information about rental code violations, how to file a complaint, and other tenant resources. We have a small private room for rent in an all-female shared house on Allegheny Avenue.