My 18 yr old niece bought an old car for $4,000 with her dad as a co-signer on the loan. Two months later, the car's transmition went out. She still owes most of the loan. The car cannot be repaired. She wants to have good credit, but can't afford a different car while making payments on the one that doesn't run. If she stops making loan payments, how long will it take before her credit it restored?