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

Boosting your score doesn’t take long, and there are services that can review your credit history and help you increase it within a couple of months. 

The thing that would deter me from this location is a background rate of appreciation of 3.12% and low school ratings.

If you are looking to keep your townhouse as a rental and find another primary , if you have kids in school , I would recommend Severna Park , Arnold , then Pasadena . ( preferably a community with either a pool and or water access .Nothing in this county pencils out as a rental unless you look in Glen Burnie and North . 

Many DSCR programs require an investor to have a mortgage history- there are some DSCR mortgage programs that will work with investors who are renting- some refer to them as first time home buyers (FTHBs)- DSCR loans are only for investment properties where the owner isn't living there. 

I am currently unmarried, no kids and recently out of residency with six figures in medical school debt.

Great to hear you're investing in Beverly, l'm familiar with the area because l went to school at Gordon College in the Wenham area.

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

This variation in training appealed to me vs. a weekly training held by the same person... feels too much like school. 

Verifying last 2 years of rental history very important!