Negative equity in 2010 but all cash flowed and all worked out to be good investments. One texas rental was only an ok investment. Cash flow is always key. There will be some down pressure on rents but little in single family. If you have a townhouse or condo that is competing with apartments that may be a problem.
There is also concerns on Helocs and then if your payments are really high you could be in trouble. I am concerned about people living off Helocs and making payments with Helocs. That is not going to work this cycle.
Population trends are an issue but in popular areas like Utah we are at least 20 years out.