I find it easier this way once you know your regulations and ROI in certain areas.  

There are a lot of jurisdictions (most of the West Coast now) that include marital status, sexual orientation, and others under their fair housing regulations.

I'm looking to buy a house in the St Pete market & have read zoning regulations, articles about STR (anything less than 30 days) and have discussed with my realtor.  

What are the best methods to independently verify zoning and land use data to ensure compliance with local regulations?

Great idea, but check your local regulations.

I don't see them ever reversing the regulations.

As long as no “healthcare” services are provided (like medication or personal care), it’s not regulated by the Department of Health.

If you're going to do it alone, make sure you your due diligence: estoppels, inspection, review, consult with a local attorney familiar with the local regulations, etc. and good luck.

Consult a CPA or real estate attorney to understand tax implications, build a reserve fund for unexpected costs, and research local regulations to ensure a smooth and profitable transition into rental property ownership.Good luck!

However, there is no specific holding period contained in the tax code or regulations and there is no "safe harbor."