Renovate, sell, pay owner, keep profit. How should I handle this?

[Jimmy Meeker]

A buddy of mine knows a lady from church that has a house that she will sell us for 80k, renovation would be 30k and we could sell it for 190k. Me and my buddy will pay the renovation 50/50 using cash. The lady that owns the house will be paid once the house is complete and sold. Once the house is sold we pay the lady the 80k, pay our selves back for the renovation and split the profit. How would I do this once I have a buyer? Is this when I would use a double close? I plan to make a contract between me, my buddy and the lady but I'm not sure about the rest? Has anyone done this before? Thanks