I have a contractor that agrees to use his own money to complete the rehab.

I am a licensed real estate agent with 20+ years experience in real estate sales, marketing and home construction.

Don't do everything on your own in general but do it once so you know what to expect and how to manage contractors better.

Like Adam mentioned, you need a thorough inspection. have handy man or a contractor attend the inspection with you to give you estimates on how much repairs would cost. 

@Joshua Hollandsworth If you don’t have your real estate license, find an agent who is willing to provide you with a market analysis of comparable properties - both in the same shape as your property currently, and in the same shape as the updated property nearby (but without the perks your property lacks).

And I understand the negative impact a bad or negative team member can have, be it a realtor, contractor, accountant, lawyer, etc.  

I do not like using the checking account to pay for contractors, repairs, materials etc because we don't get any benefits, miles, cash back. 

should we setup an LLC or any other kind of business, knowing that we will use contractors for the biggest items?

Account ClosedDo you have a real estate brokers license for the state of NY?

In my market the cost of a general contractor willing to play ball with 203k is such that BRRRR will not work since you will not have sufficient equity after financing the cost of said general contractor.