They did everything they could to discourage rentals short of banning them which would have cost too much to file the legal documents.

Absolutely not (Because I'm about 1.25 mil short of the 1.25 down)

I’m looking into purchasing a property in Kissimmee FL for a short term vacation rental.

This could be a good opportunity, just don't sell yourself short. 

Spending an hour with a CPA who understands your overall financial situations would be time well spent, but there are some general rules of thumb:If you hold the asset for less than one year, your profits are considered short term capital gains - which are taxed as ordinary income at your standard tax bracket rate. 

What are the bare minimum requirements I should request in a written agreement/legal document with this individual to best protect my asset in case his investment fails or falls short.

Option 1: I will receive only the rehab, hiring a contractor and ask the buyer to pay the property direct to the ownerOption 2: I will receive full payment (property+rehab) and my company buys the property a resell it shortly to the buyer

Pending sales in DFW dropped like a rock vs. prior year, and since sales lag pending contracts by a month or two I would expect that it will start to affect the sales numbers shortly. 

From what I've read around BP, people seem to have a tough time with Airbnb in Miami so just have him check and see the laws surrounding short term rentals.

If you are buying for the long term and the numbers make sense then I wouldn't worry too much about the short term market, that's just me.