But the areas are so big and diverse.. like different ethnics, quality of neighbors, quality of schools and etc. all in one bracket of low income area.

Daniel it's hard to comment in detail without knowing your goals.Buying houses in multiple states gives diversity but also you will have likely many PM companies to look after.Depending if you are after lower income houses with higher rents to purchase price then you will also run into lot's of problems managing from afar. 

Credit diversity (Mortgage, auto, credit)6.  

Biggerpockets community is truly awesome through their diversity (buy and hold, wholesalers, bird dogs, commerce, developers, flippers, agents, etc).

As you can see there are lots of diverse interests in the forum.

Employment diverse or dependent upon a single employer?

Bring cash to the closing if you have to and get rid of the diversion.

If you are in real estate, spending your time on direct mail may feel like progress, but it's really a diversion from what you should be doing.  

The main road has a lot of diversity with restaurants, banks, tourist shops, ice cream, etc... 

I have since than bought 4 more rentals (total of 5) with the goal of 5 more in 18 months.You will love the diverse community and all the resources.