Listen to Streakn! Don't let enthusiasm cloud your judgement. Make sure the contract is IRONCLAD before you sign anything. Take it to a lawyer to look over. Try to make payments directly to the lien holder, because once the seller has the money in his hands, anything can go. I have experience in this matter, and it's nothing but bad. Most who get screwed in these situations are suckers... including me. Though I did what I could to limit the potential loss, it turned into a loss nonetheless. The best thing I could've done was stay away from it, build up my credit rating, and get a loan.
One other thing... whether the leasor or the leasee, there should be no 10-20% of the take off the top. Either the guy wants to get out from under a bad situation by leasing it to sell, or he just doesn't want the payment anymore. Either way, he shouldn't profit from his mistake. Both parties are doing each other a favor.
-True independence can only be gained if you're trully independant.