If we were to make more than three loans per 12 month period secured by properties in AZ then either we would need to hold an Arizona commercial mortgage brokers license, or we would have to make the loan through someone licensed as a commercial mortgage broker by the state of Arizona.Any more detailed or technical questions would probably have to be answered by legal counsel knowledgeable in regulatory licensing in the state in question, or the state licensing board itself.

If you converted your SFH to a duplex, were there any unexpected problems/surprises on the legal/regulatory side, like being unable to rezone the property or get a rental certificate? 

Regulatory burdens are likely to go up, and I think asset prices will remain artificially high due to loss aversion.

This is a huge topic, @Vincent Billera, and one to which the response has dramatically changed in the last few years.Prior to regulatory changes, unless you knew the right people (colloquially were a 'member of the right country club'), you were shut out of the option to invest in anything but that which you can personally afford.  

Explore the feasibility of an assisted living or senior living facility, keeping in mind the regulatory requirements and specialized knowledge needed.Subdivision and Mixed Use: Consider subdividing the land to develop a mix of townhomes or apartments alongside commercial spaces.

Have the seller warrant that the property is currently permitted to operate as a mobile home park and has all the necessary zoning and regulatory approvals needed to maintain such approval.2.

You can learn more here: https://www.ashevillenc.gov/ne...Here's where you can find what is inside Asheville city limits: https://www.ashevillenc.gov/de...Here's a recent update about NC legislation that may soon end Asheville's regulatory power regarding STR's: https://www.biggerpockets.com/...

It is unclear whether they would like to later propose statewide regulations for short-term rentals, but they intend to first remove regulatory power from local governments.

We are indeed living in strange times.In United States constitutional law, a regulatory taking is a situation in which a government regulation limits the uses of private property to such a degree that the regulation effectively deprives the property owners of economically reasonable use or value of their property to such an extent that it deprives them of utility or value of that property, even though the regulation does not formally divest them of title to it.

I think tiny / shipping container homes could be a good idea for housing homeless veterans or to use for sober housing.I'd guess that if you got the right support groups behind you, that could grease the skids for both financial backing and help getting regulatory roadblocks cleared.