Sub2 existing w/final balance at resell

Heard this and wondered if anyone has done it and if you could help with contract?
Owner doesn’t need $$ and is willing to Sub To existing mortgage. But agreed price is $8k more than existing mort. Seller is willing to accept the $8k after resell of remodel. I need the cash flow to remodel. Basically this is a No $$ Down, Sub To, final balance at resell in 6-8 months. How do I write this in contract? Any ideas?

Spell it out in the contrat the way you just did in the post. Property being sold subject to existing financing paid in the following manner: Purchase price to be balance of existing mortgage…approx 200k…payments of approx 1500 a month plus an additional 8 thousand dollars. Buyer will have 8 months to pay the 8k or at time buyer sells property which ever comes first…With a little more info I could make this work more in your favor.
Good luck, Darin