What kind of contract do I write when someone stole money from me and they want 60 days to pay it back instead of going 2 court

After I investigated and received evidence, my ex roommate finally admits to stealing $600 from me earlier this year & has unpaid bills in the amount of $500. He would like to sign a contract to pay this money back within 60days, instead of me taking him to court. What kind of contract would make this agreement legal and binding? - Is this your question? Add additional information