A cosigner is generally used on a mortgage where the applicant would not qualify for the loan.
Here’s how it works. For example, you want to get a mortgage for $100,000 on a home you are buying. The bank won’t lend you this money because they don’t consider you to be a good credit risk. What can you do? One solution is to get a cosigner. This is someone, usually a family member, who will guarantee that the payments will be made. If you stop making payments, then the lender will come after the cosigner. This is a big responsibility for the cosigner, and not everyone is willing to take it on. The cosigner must be someone that the bank considers to be a good credit risk since he may be called on to pay for the house if you can’t.