Legal Question in Credit and Debt Law in Ohio

Depending on the amount of money and the circumstances, you could start with a polite businesslike letter explaining the situation and asking to be paid back. You can always negotiate payment terms-- over time, interest rate, etc. If there is no response to your letter, you could try mediation with a neutral to help resolve the problem, or ask an attorney to write a more formal letter seeking payment. As an utter last resort, you can file suit, perhaps in your local small claims court. If you get to a suit, your friendship is probably over, so try other remedies first.