I suspect this will be one of many experiments conducted of this type.I’d recommend that you get your license if you go this route.

I recommend addressing soft spots in the floor by replacing the subflooring, rather than covering them with new flooring, as it ensures long-term durability.

I would greatly appreciate any attorney recommendations who could help identify and form the proper entity for our situation.

I have couple of questions from people who are well versed with this zip code and can offer valuable suggestions / recommendations, if any. - Is New Port Richey a nice area to invest  from a buy and hold perspective? 

I am not sure why is that but you have to be careful on what are the agreement on that contract.In this case, I would recommend to get involved with a investor friendly realtor who will help you as it could be many issues during the process as the titles are not clean in most cases and many variables have to be checked. 

As for rent collection, bookkeeping, etc I recommend you go through some online demos of different products to see what works best for you.

I would also recommend that they have sufficient 'skin in the game' IE additional down payment above and beyond just having lived there a while. 

I recommend doing massive due diligence if you are taking on the risk of trying remove a tenant and move in.

And does anyone know anyone or recommend an ADU contractor or appraiser in my area (90031). 

I can recommend a local attorney.