I’m not an out of state investor myself, but I am a native of Memphis so I’m part of the “team on the ground” so to speak for a few investors abroad.
I have to second the notion that it is well worth flying into your targeted market to get a good feel for the area as well as shake hands with your prospective “team”.
While selecting markets, most of the top Midwest cities have been mentioned here so from there it is a matter of looking into job growth, development, vacancy rates and weather patterns. Oddly enough, cities with high crime rates tend to be at the top of the list for best cash flow markets like St. Louis and Memphis. You can’t expect much appreciation in these areas, though.
Once you’ve selected a market, next up is selecting a property. If you don’t feel comfortable forming your own team (someone to finds deals, PM, contractor, inspector, lender), then you may want to consider going the turnkey route for your first few ventures. You can do most of your due diligence from afar looking at Trulia’s crime map, compare asking rent rates on Zillow nearby (and how long they’ve been listed) and looking at the street view to make the block.
Best of luck on your ventures!