We have our Guide Book on the counter in the kitchen.People like to have something to look through, plus other guests leave flyers from places where they ate etc. with notes like, "Great food" etc. written on them. 

They saved him some money by helping rip out a lot of what was likely going out anyway, they hauled it away (granted, they dumped it on the neighbor, but it's still out of there) and they didn't even leave any personal posessions.

For example, if a tenant refuses to leave at the end of a lease, how difficult would it be to get them out?

I think you are concerned about seasoning requirements for cash-out refinances here.

The idea of letting someone bring their own RV, live in it a week or three, and then leave with it and their mess is great.  

One thing I would mention though - doing STR just to save taxes often leaves you operationally unstable or too detached from the management to be successful.

Monthly cash flow, retirement, leaving your job.

You will not see $1.3M you will only clear the difference of that 25% ($325K) minus taxes, Seller/Buyer fee's, attorney fee's might leave you with $180k amount split 2 ways so $90K each.You could take out a Heloc and pay him to walk away from the home so you can turn it into your home plus rental.

Should I stain these doors and hardwood floors a dark expresso color, or lighten them, or just leave them alone?

Regardless, the person with the umbrella policy has no big concern and should not lose a wink of sleep.