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 for an apartment takes on the financial responsibility for a lease.Learn how having a cosigner can help someone get approved for an apartment. A comprehensive guide to Washington State rental application and screening laws. When do I need a cosigner? Our Lease Cosigner Agreement form is customizable so that you can include as much or as little additional information as you would like. Com and click on the "Vacancies" tab.