PCB and Destin are two distinctly different areas, and I'm not sure which market you'd like to focus on. 

The ozone breaks apart mold in the room, and clears various scents.  

There are some distinct differences among the areas that could sway your decision.The northernmost section of the OBX runs from Nags Head to the Virginia border.

This distinction may affect how you report these expenses on your tax return.

It is distinctly possible that he could be an employee instead.

While there is no statutory holding period required to qualify for 1031 treatment there is a distinction between buying property as inventory with the intent to resell it (this does not qualify) and buying property with the intent to hold for productive use (this does qualify).  

IMO that's the key distinction, the big dilemma and the first question you should answer.  

Does that mean as far as HUD's fair housing is concerned, there is no distinction in their policies and guidelines on how SA and ESA owners are to be treated/screened/verified by landlords?

The zoning distinction is attempting to preserve some housing for locals, but also help provide some accountability for STRs when they have the rules and amenities of HOA communities.

Rather than commingling funds and ownerships, separation using distinct LLCs could have some benefits.