Look for markets that have growing populations, growing jobs and modern, diverse economies.

The Midwest is solid, affordable, and can be diverse in the RIGHT areas/regions.Investigate different states and areas, find a few you like, and then locate some great people to connect with that live and work there and can help you invest there.

Currently the average rental amount in Tampa is $1350 with a diverse community that makes this market very appealing to investors. 

This past track recordM along with future indicators (vacancy, population growth, quality and diversity of jobs, supply, etc.), places the investment as perceived low risk and high return.  

Hold your 401K and enjoy the diversity.

@Blerim Capric Garfield is very diverse and it also has a strong Polish community.

I don't have stats but two things I look for are diversity of economy (ie no 1 business towns) and proximity to larger-anchor cities like KC, Detroit, Chicago, Indianapolis etc.  

@Joshua Heath You touched on the perceived diversity of Charlotte and that's something I am trying to better understand (I moved here last summer).

I actually do have diversity from the standpoint of bedroom count with the two I have and the third one being built is almost double the size of the current four bedroom.

Phoenix is a very job diverse market, massive population growth, the standard of living is relatively low (aside from real estate), there is a major supply shortage of "starter" homes and costs are high to build new homes which all create higher property and rent prices.