@Justin, I wrote (2) VA loan articles for BiggerPockets (just search "VA loan" in the search bar) that will be able to help with any questions you have there.

Pick one zip code, or one neighborhood and a specific type of property and focus on that for a while. 

I can't recommend any books, but for foreclosures and tax deeds, a good place to start is to get all the info you can from the sheriff or court house clerk who puts on the auction, and read the state's revised code/statutes on the subject.

I am currently finding a property, then staring at various maps and essentially guessing as to where it falls, then researching codes and regulations in that area.

People packed into clubs, restaurants, bars?

We've removed a lot of K&T over the years due to Insurance mandates & code requirements.

https://fox2now.com/news/list-states-that-have-closed-restaurants-and-bars-to-dine-in-customers/

When building a duplex and i'm the GC do I need an engineer to be involved or can I just get by with an Architect stamping off on my plans and making sure they are up to code? 

I am not allowed to broadly advertise specific commission rates; however, I am allowed to mail postcards offering special commission rates to areas where I've recently sold or if they give me permission to target a specific group (like non-owner-occupants in a specific zip code, for example). 

My contractor is sending me photos of the work almost daily revealing huge structural defects, damage from rot and termites, and he's telling me the inspector is telling him there are a ton of code violations that are going to add to the cost, for example the HVAC ducting needing to be totally redone.