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. Wondering what's the purpose of a cosigner in NYC?Actually, that will make a loan or rental application more attractive. A cosigner can help you get approved for an apartment if you have a poor credit history or are unemployed. When asking someone to be a co-signer on an apartment lease, first explain your situation. It's important to note that property managers can still reject your application for rent even with cosigners. Typically guarantors will need to produce the same documents as tenants, as well as fill out an application and have their credit run. Renters need to have a social security number. A guarantor is a person or a company who will co-sign on your lease in case you do not qualify to rent an apartment in New York on your own. The guarantor is not a tenant of the apartment and will not live with you in the unit.