Being a real estate professional allows you to treat the income as non-passive, allowing higher high income tax payers to pay less in taxes.

You would have to go after the one individual for non-payment and you could only remove the other three by going through the legal process like you would for someone on a verbal agreement, which puts you in a he-said, she-said situation. 

That shouldn't necessarily be a differentiator when choosing a lender, as evidenced by the boom of the DSCR lending industry....non of which are FDIC insured.

Wanting to evict them are a tenant is late for a week or waiting months of non-payment to start the eviction process.

For the HVAC, I'd just question if that's the correct and best way to go about it, but I'm not an expert, but certianly you won't get interest listing a unit for rent or sale without HVAC.

The most common is leaning on your agent for their expert advice.

Just like any aspect of real estate investing, non-consumer lending at a large scale is a relationship business. 

You really have to be an expert and outshine the competition here.

Although not a an Airbnb Expert as I once was but from making good money on airbnb in the early years and being a landlord most my life.Keeping it Simple.

Now it appears your cleaners might be cleaning non-STR properties also (home owners).