<prompt> Human: I intend on getting it back plus interest. What is a reasonable in terms of interest and whats the best way to go about doing the deal? He offered to put it in writing that he would return the money within 4 years.  <response>: If you cant consider it a gift, forget it. My GF loaned my best friend money to pay for college tuition with similar promises in place. He paid back about 10 of it total. 