Each state has it's own laws concerning these matters. What state is the Unit from? That may be the state laws that need to be followed but I am not sure. Did the loan agreement have a witness? Did the loan agreement have a payment plan of any kind? The military may have it's own laws in regards to this matter, especially between people of different rank and/or depending on if one is subordinate to the other. Tell your husband to keep all documentation from the friend in reference to the loan, any letters or emails. If the person decides to go against the agreement small claims may be the way to go if the amount loaned doesn't exceed the small claims limit.