I would start backwards from your purchase price and financing to narrow it down, go with a landlord friendly state and try to leverage anyone you know (family member out of state, friend doing BRRRRs out of state, etc) - that should narrow done your market quite a bit.

I have heard from others, including @Karen Chenaille that Vermont is very STR friendly. 

I also suspect the seller's friend rented the other unit because the rent is cheap and the landlord is a pushover.I would look at this entire situation carefully.

I am helping a friend with a property his mother has some investment in.

Two of my close friends just purchased apartments in downtown Punta Cana (which are under construction) and we just built in another beach town called Samana. 

We're mourning the loss of friends and neighbors, some of which haven't been found yet, not to mention favorite places, small businesses, animals, you name it.

Invasion of privacy, unclean and rude house members, maybe if they do drugs or smoke or are party animals, unwanted friends of theirs visiting at odd hours, clashes of personality

95% of the issues with LVT/LVP installs are from user error. 

The company owes me (and a friend) over six figures each.

That said, it sounds like the software they are using may not be as STR friendly for them to manage your place while also giving you, the owner, the visibility you're looking for.