An instalment sale agreement between you and a credit provider allows you to buy a vehicle or asset using the principal debt, which you repay by means of regular instalments over an agreed period, with fees and interest.
Installment loans can be a valuable financial tool to help cover significant expenses. When repaid responsibly, they can help build or improve your credit score. The most valuable way installment loans impact your score is by allowing you to establish a track record of consistent, on-time payments.
Being a co-signer itself does not affect your credit score. Your score may, however, be negatively affected if the main account holder misses payments.