Where to locate regulations/rules for hard money lending business if they exist? 

There're IRS Regulations that allow for an exception ("reduced maximum exclusion") under "unforeseen circumstances."

@Richard Arden I believe you can find the information in the zoning regulations.

While home builders have been classified as "essential workers" in most areas of the country, regulations still require fewer people per crew, dragging out project times.

This is our first home we've purchased, so we do not know all the regulations which is the reason why I asked.

All that to say investing in STRs in a market as HIGHLY regulated and restricted as Nashville is not the best use of your time or money. 

Plus, the licensure courses usually just teach you about the laws and regulations to keep you out of "realtor jail" as my colleague puts it. 

I would also want to regulate who can access it so the public isn't involved.

You'll have to apply the tangible property regulations to determine treatment of costs.

Most likely, the area won’t have enough data for an appraiser to provide a fair comp analysis for a flip project, thus potentially leading to a loss in returns.The new laws for CA beginning this year have made ADUs a popular topic in the real estate world because of the relaxed regulations.