George,
#1 - Have you seen the property?
#2 - If answer to #1 is no, make it yes, by going to property to verify all assumptions. If you cannot do this, have someone you trust do it for you.
#3 - Verify/confirm rehab estimates/costs and actually meet the GC who the buyer intends to do the work? Are they real, licensed, qualified, to do the rehab?
#4 - If an investor/buyer/borrower wants me to fund their project, they can expect me to be VERY involved in what they are doing with MY MONEY! Once I confirm the numbers and validate the deal, trust me, I will ONLY release rehab funds at certain, pre-defined stages, which normally track the permit process; carpentry/framing, concrete, electrical, plumbing, drywall, finish, final CO, etc.
#5 - Oh, let's not forget..., What experience level does the borrower have? Are they doing the GC work themselves, or are they going to hire a real GC, and, have you met the GC as well?
In summary, there are lots of snakes and alligators ready, willing and able to deprive you of your hard-earned private or hard money capital. Deal with the above, make sure the contractor is licensed and insured, make sure you are named as additionally insured on the hazard insurance, which is most definitely reflective of the fact that the project is a construction work in progress, be a member of an LLC who owns the property with an operating agreement, etc.. By all means, use of an attorney who understands real estate and these types of deals is a minimum requirement. Best of luck to you and the project!