? on a deal I am working on.

I am working a deal where I purchase at 550,00 the ARV is 915,000 the rehab is 150,000.
The owner has agreed to hold the deed while I do the rehab. The house is paid off so it is no big deal to him. To do this he wants 55,000 up front. What type of contract should I put together to do this type of deal?