seller financing

[Brian Whelan]

I'm structuring an offer for a seller who has indicated he may be open to seller financing.

He's an older guy so wants it to be relatively short-term. I think I can make the numbers very attractive for him. Asking price is 250K and I want to offer an approx term of 120 months for payments. 

Just wanted to get some feedback on what a typical deposit amount to offer in this situation would be (5/10/20%???) 

Also, how much would a typical seller reasonably expect to make above the asking price by agreeing to financing it over a period of 120 months?

Thanks, as always!