If you were to rewire the entire property, which is probably the best thing to do long term, would that allow you to upgrade the units to central air, mini-splits perhaps? 

Short of that: you can air pressure test the water system and bring a good sized generator to test electrical components.

They are 3 bedroom, 1 bath, central heat and air. 

(trashing the property, not changing air filters, overlooking repairs, unauthorized pets)6) What is your process for handling service requests?

Most of the time if you can prevent the cold air from getting to the pipes then they are less likely to freeze.

I sold miners (mostly open air 3-4 GPU AMD based).

This is a mil to mil couple, Army/Air Force.

There was a definite arrogance in the air, and I think they assumed I was a lowly assistant because they were almost trying to impress me with their “knowledge” of how they could legally enforce this chicken nonsense.

Doubtful this is nothing more than hot air.

I have experience with both single family, condo and townhome air bnb options in SEATTLE.