What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

(Minimal competition, high demand, and 20 year operating history with repeat & longterm clients) Agreed!

Mortgage notes require due diligence on borrower history and property value.

A general rule of thumb though (not a hard rule) is that if a market has a prolonged history of vacation rentals such as towns whose commerce is very dependent on tourism like beach or mountain towns, then there is a good chance than those towns have established their airBNB regulations decades ago and are likely stable.

Verifying last 2 years of rental history very important!

I understand that is not your history, but that is what you sound like today, IMHO.While the response was very weird and did not provide a date - I would not jump to the conclusion it is a ponzi scheme. 

Based on my previous investing history (completely unrelated to real estate), I would describe myself as a buy-and-hold kind of guy.

I only bring it up to say it can be done, even with a group that doesn't have a long history in that market (the two deals I mentioned were the first in the market to acquired by a Sumrok student).

Most S8 tenants have a history of bad decisions, often having convictions, evictions, bankruptcies, chargeoffs, collections, garnishments, etc.

In other words, if there are attorneys who can afford to specialize in just prosecuting dog owners for dog bites - then good luck defending against them.What I learned when I was studying law, was that if there is any history whatsoever that a dog has ever bitten someone or a dog before, then no matter the circumstances, if they bite again - they are automatically guilty.And, even as a dog lover, you and I both know that some breeds are more likely to bite than others.