I couldn't even calculate the odds.Your best protection is to know the law, obey the law, treat your tenants honestly and fairly.

Treat them no differently than any other company you work with. 

The best way to handle private money or private lenders for flips is to keep it simple and treat them just like a bank.

I've been treating it as if it were a rental property occupied by a tenant. 

In theory and in non-Covid historical times,  you’re right that your former owner will be treated like a holdover tenant and should be evicted in 1-2 months.

It will be treated as a commercial loan. 

.- I called my pest control service, the they came and treated both units, the "messy" tenant showed up to unlock the door for them and left.- The pest control technician called me from UNIT A, advising that there were unsafe / hazardous living conditions, and proceeded to send photos. 

Added 1 bedroom making this a 3/1, new roof, sealed and treated foundation, cleaned up exterior, painted and refreshed the interior What was the outcome?

ADUs added to SFR zoned property in an area with many duplexes to quads, is often treated as a duplex for appraisals and financing.  

I've been treating it as if it were a rental property occupied by a tenant.