You don't need to know everything to get started; you need a foundation to build on, and the rest will come through experience and then refining your education.You can build a basic understanding of investing in 3-6 months.

I'm trying to understand how frequent this is.  

There's no precise figure because no one will understand your STR or market as well as you do- or, as well as you will (with time).

I don't know the Baltimore market but have a friend who is a very savvy investor there and maybe he would do some coaching to help you understand which way is up.

This will help you understand your options and decide if it's the right time to hire a pro. 

This is something I aim to understand more about.

Best way to understand this is research appraisal standards and means. 

Their program is simple to understand for the most part.

I don’t understand how this isn’t a clear-cut case.

But consulting with the town would be good to try to understand what they're permitting process is like.