sometimes you don't need anything in writing...we have customers all the time that don't sign the lease or any paperwork...just as long as they have made a payment there is proof of a contract there....you could say that we had an agreement that we split the rent and since he didn't pay his end i'm taking possesion of his car to make up the difference (sell the car)....you would need any way that he gave you money...via bank statement showing you depositing his check for rent...or the rent lease...but i would think this would make it more complex and then you would definatly need a lawyer at this point...i still say consult dmv first and get exact details of what you need...