Then you can concentrate on the four plex because you'll have enough money to pay someone to manage it for you and have them absorb all the management headaches.This is just my 2 cents. 

Now I can buy one type of paint for all the houses, and some other small things, but having 50 units is 50 separate units. there are just better ways to do things 2a concentrations of geography.

If you have a hard time concentrating, then read "One thing" by Gary Keller to help you stay focused.

What are the areas with high concentration of blue collar workers to fulfill the above-referenced projects? 

Whatever RE track you decide to pick, concentrate on it until you fully learn it.

So again, you need to decide for yourself what area of real estate you want to concentrate on first - get educated in it and start doing it, then pick up the next niche in RE and do the same, and so forth.

Now I concentrate on being the visionary in the company while having others do the implementation of my "Vision".As I am typing this, I'm watching my VA's on a separate laptop in my office skip tracing high equity foreclosures.

When renovating concentrate on the kitchen then the bathrooms and then the floors. 

Florida I concentrated on multifamily but I don’t see many multifamily properties in this area.

If you google "real estate" +business +college +degree, you'll find a number of universities that offer degrees with real estate as a concentration.