Structuring Joint Venture Deal on Flip

[David Goossens]

Hi BP,

I'm working on my first flip deal and would like some advice on how I should legally structure it. Here is the scenario: A family friend is retiring and moving out of town. He wants to sell his house, but it is outdated and in need of some serious work. He he has no interest in doing the work, or even contracting it out, and was considering taking a loss of the property for a quick sale. Instead, I told him that I would put up the money to fix and update the house in exchange for a portion of the proceeds after the sale. He would get an agreed upon sales price plus 20% of the net profit, while I get the remaining 80%. My question is this: What are some ways I can legally structure this deal, and is it possible to set it up so that I get paid straight out of Escrow? I don't really want to risk the due on sales clause resulting from a subject-to transfer, and getting a hard money loan to buy the house outright seems like a waste if i can instead setup some type of joint venture. 

If I didn't provide enough information, please let me know so I can be more detailed!