$135 a foot and an 18 month wait to build and the potential for materials to go up an additional 30%...

Something as simple as you providing the materials for the work and/or the tools can classify a person as your employee (state specific).

That means scheduling the work in the right order, making sure materials are on site for the subs when they need it, and being available on site to make sure the work is done to your standard, and to resolve any problems that will definitely come up.I'd definitely find out what permits are required. 

Any suggestions/recommendations about solid learning materials (book/podcast/youtube…)? 

They seem to require high quality materials and  craftsmanship to maintain a level surface.

At that time, RCA’s general contractor was given access to examine the units to pre-order all the materials needed for the 4 apartment renovations.

So you need to make material changes to your listing to justify duplicating it, not just because you want to get around some Airbnb policy.  

Because of this, they're purchasing their own supplies/materials with very minimal labor expenses.

You need to pass "material participation" test and personal use test, but that's for your future tax professional to explain.Yes, bonus depreciation is possible, but only on the current value of the personal property and land improvements.

I think you should at least get all your finish material pricing figured out first by going to the material stores and also getting quotes.