Most state laws require lenders to allow that HOWEVER the LLC has no credit history so the lender is allowed to keep you responsible for the mortgage.

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

You only need a place to track tenant information, payment history, maintenance, etc.

I get the concerns about liability and title insurance, but I’ve had success by thoroughly vetting the company’s history and securing protections like hold harmless agreements.

So, unless there is a history of STR income (usually at least 12 months), most guidelines won't allow STR income to qualify. 

This required previous rental property ownership history and a personal balance sheet the bank used to underwrite their risk.Due to these barriers to entry, I have been exploring a zoning change from B1-1 to RM 4.5 thinking the change will open up the pool of potential buyers with the ease of residential financing.

You can go and look at the history of all the auctions once you register and see how the bidding went, and whether the lender or a bidder won each auction.  

I was already a licensed agent for 3 years @ that time, I was already doing a short-sale across the street, asked the seller if he knew anyone in the neighborhood looking to sell, & the rest is history as they say....I ALWAYS wanted to do a fix & flip, & this was my BIG CHANCE!!

I screened Tenant B per usual, although they have the least rental history of anyone I've rented to and are getting a bit of the benefit of the doubt based on Tenant A having been good (plus they have a guarantor, the mother of both tenants).Tenant A is moving out half a month before their year-long lease ends.

Well, I’d say that the free market is the most moral vehicle humanity has had in our history.