They are over 55 with limited income so I'd like to keep as economical as possible. 

Charlotte, Raleigh, and Wilmington are good markets with promising economic bases.

Indeed, economic experts predict the country can withstand four rate increases this year, versus the old estimate of three.

While neither I, nor those with far deeper economic credentials, can tell you when the train will stop, or whether it will fly off the tracks at tight bend, the further real estate prices diverge from underlaying economic fundamentals the greater the possibility the ride comes to an abrupt stop - even if it later picks up the pieces and gets back on the track.When the music does stop, there will be a lot of folks looking for a place to sit down.

So I think there is a solid chance the city will make an economic come back in the next 10-20 years, but in the mean time the numbers still work under current market conditions.

Is it due to bad management, economic or area.

The economic value of each is drastically different.

Modify analysis to include the following issues with low income, slumlord properties;Budget for building compliance, building and fire codes;Increase vacancy rates, tenants walk off.Legal fees, not just for evictions and collections, but for government matters with violations.You're more likely to have law suits as well, legal aid is free for low income folks, and generally if they bring suit you'll lose, even if you win, you don't really win.Factor in the economic aspect of your ROI, the additional time, effort, hand holding and counselling required with low income tenants, don't forget police calls. 

Economically, it is right up there with the most powerful countries in the world right?

It's extremely competitive to find flips and there are only a few small pockets where rentals make any economic sense.