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 well qualified co-signer with great income and credit score can lower the landlord's risk from a poor credit score or questionable income.Wondering what's the purpose of a cosigner in NYC? Actually, that will make a loan or rental application more attractive. Please make a note on your application if you do not have sufficient rental history. Signer or double deposit may be required. Guarantors help tenants qualify for an apartment. They promise to cover rent and other expenses if the tenant fails to do so. They're required to fill out a separate application with the appropriate fee and the cosigner agreement is typically notarized.