We were approved for a FHA, at 200K, 0 PMI, , 0 down and traditional at 280K, 4.5%.

You'll definitely want to have a WV Attorney - due to different Laws WV as compared to Texas. 

High tides raise all ships"  - this is why you're seeing traditionally dead markets growing.Never a better time to be a flipper.

Yes if your attorney has some experience with RE contracts, that should be good enough.A Real Estate agent can help with comparative market analysis to help you confirm you are getting a good deal.

What are your thoughts on using cap rate vs. comparable sales?

The best suggestion I have is to spend some time comparing your units to the others in your immediate area and don't over-improve as often there is a natural price "cap" in the neighborhood and regardless of the small upgrades that really do improve the living experience, it's hard to make them into the rental rate if you are near the top of your market.

That is why I am looking to make something work without using a traditional lender.

If you're not adding significant equity, just seek out a traditional loan with no PMI from day 1.

Tourism is an historic well established business there and make a comparison Mexico Vs Colombia is like compare a tropical island vs a desert .

My question is, in calculating comps what do I use for the comparables?