You can get a bunch of employment and job growth numbers from the Federal Government of Bureau of Labor and Statistics.
http://www.bls.gov/eag/eag.ga.htm
State searches are to the left. Towns that are heavily at risk are what I call ONE ECONOMY towns.
This is where one business is propping up most of the economy.If that business goes most of the other businesses will follow and the town will start dying off and people will migrate elsewhere.
Once vibrant towns 30 years ago are now all but vacant and many will eventually cycle and spring back.With one economy towns it's very important to know what that businesses plans are for staying and if they own or lease and when it's coming up for renewal.
Many investors stay only in big city cores for what they see as less risk. Suburban to rural can be great investments if you do your research and know what is going on and helps especially if the local economy has many types of trade propping it up.
This way if one leaves or fails the government can usually get something else in to cover the shortfall.There are many,many other things you can check as well that you do for planning on larger commercial projects.
For house rentals I don't think it's necessary to go real deep with it.