NEW YORK (AP) — Credit scores are complicated and because rating agencies consider many factors, the process of improving them can look different for everyone.

When Willard Carpenter, 68, wanted a loan to open a new business, he realized that his credit score was not high enough to get approved. After checking his credit history, he found several issues he needed to solve.

Carpenter's credit was heavily affected by credit card debt that his father left on their joint account after his death over a year and a half ago. He's also had no credit cards for at least 10 years — he stopped using them...