Maybe you concentrate on looks too much.

Yes, there are podcasts that mention avoiding high crime areas, but there are also podcasts where people specifically work in areas that most people avoid... primarily for the reason that most people avoid it, and they have no issue with it.If you are planning on managing the property yourself, then you need to know the kind of tenants you want to have, and that will help you narrow down which kind of neighborhoods you want to concentrate on.

If it's just you, no partners, buying rentals with residential loans and little equity, probably you should concentrate on growing that first and getting some equity before you worry about LLCs, business accounts and asset protection.

Concentrate on one niche in RE investing at a time. 6) As far as your friendship/partnership, if your and your partner(s) to be objectives and long term goals are aligned and your attorney spells out clearly each partners' responsibilities in the operating agreement, you should be fine. 

If you are in a low paying job concentrate on increasing your income.

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.