This reminds me of a wise statement my Father taught me and it goes a little something like this "Never a lender or borrower be" OK you may have a leg to stand on if if the agreement is notarized and witnessed , take off the previous owners Tags licensee (plates) as these are his/hers property. You may also want them to empty any contents thhey own keep this in mind " Anything bolted to the car must stay and go with you all else (not bolted) they have claim to. If it was me I would try to work it out if this pweson is a good friend, they must be if you were willing to help them out !! In the future tho practice my ffirst part of this post For the good of all invo0lved
Good luck to all.
Rick