Ask what position will your loan be in?
What is the ARV? Show me the comps, what is the budget, what are your contingency estimates? What is the LTV with your investment, how much skin does the rehabber have in the game? See pictures or sales flyers or website listings of past properties, does this one fit the profile of their past experience, in other words are they doing a rehab on a property that they have had experience doing in the past? Rehabbing a fire damaged house or hillside property may be different that rehabbing 3/2 ranch in a blue collar neighborhood.
Exit strategy and fall back plan. Timeline estimates, including how long your money will be working, are there any minimum number of months they will pay you? How much time will the rehabber need to buy me out if I should need my money back at the end of the agreed upon terms and the property has not sold?
Get a deed of trust ( rehabber to record or will you do it yourself?)
Promissory note ( vetted by your attorney) Will you get monthly payments or paid after sold?
You must be named as additional insured on the property insurance.
After the first time working with a that rehabber its easier, especially if you have a good relationship and the communication has been good. I have built a lot of trust with my go to rehabber, he appreciates my money and takes very good care of it and I try and place my investments with him whenever possible.