Next steps are to put down a roll of plastic to prevent moisture or wet floors. 

I had them drive past and refuse to stop even when a concrete truck was on the way.

Make sure its on a permanent foundation, has concrete pillars, skirting and axles removed and in some states require hurricane Tie downs. 

Maybe concrete single-family 1-4 units depending on the price point and cash flow.Also there is no real MLS in Puerto Rico you need to find an agent for each area you want to look at.

Quote from @Paul Gupta: Hi, in California, For jobs requiring a license, there was CSLB (contractor state licensing board) which would give either a General Contractor license, or specialty licenses by trade (~60 specialties such as concrete, welding tile, ) https://www.cslb.ca.gov/about_us/library/licensing_classific...My Q: does Maryland and DC area have similar requirements? 

And you still have to demo the concrete slab (I don't think you have basements in TX?)

Oh the pink and beige house with the tall concrete fence?").

Since you are not doing super high end finishes as mentioned, doing high end flooring and all other stuff just above builder grade does not warrant tile or full wood flooring. 

The property has two residential units on the second floor and first floor is a retail space.

For rentals, would a single floor or two floors makes sense?