Where can I get info on setting up payment schedule w/interest incl. for loan my mom made to relative?

My mother took out bank loan for a relative and just gave him the money. Now problems with payback as no interest & closing costs considered by loanee. Where can I find a table or payment schedule so I can set up a repayment plan that will be fair to mom. Then can we file it somehow to make it legally enforceable, if all parties sign?