In addition to the ones you mentioned and the others shared, I would also look for some diversity among industries in the area.

In general, aim for markets with growing population, diverse economy, and low unemployment.

A little frustrating, but given the diverse employment base in the DFW area, I guess it's not all that surpising. 

No one should underestimate the importance of diverse income streams to a goal of being able to withstand financial setbacks. 

Those trends being net migration, jobs & employment, industry diversity & other aspects along those lines.

I do believe NYC will bounce back, due to the diversity of all the businesses here.

Lubbock is also a solid rental market and has a fairly diverse economy. 

Industry diversity is also important to consider in my opinion, as population growth and supply of housing can all be affected if a city is reliant just a few industries to provide jobs.

From a macro level the region is strong and diverse economically, while still being fairly affordable for the rents a good unit will demand. 

The most important things to look for in any market are growing populations, growing jobs, modern economies with a diverse employment base, business friendly climate, low property taxes and favorable landlord tenant laws.