Where are these properties located? Location matters. If they are in an area of the country/world where folks will do well--and in my opinion a place with natural resources and a lower population will do bettter-- it's one thing, but if the rental units are in a depressed and/or overpopulated area I'd be more wary.
I've considered incme from rental properties to fund my husband's and my retirement and had the same concerns. For what it's worth, I believe that we have NOT seen the bottom of the housing market. Not by a long shot.

I would like some input about keeping or selling some rental property I have. I have three duplexes which I bought starting in 2008. My mortgages are more than the properties are worth in two cases with 7 1/4% and 6 3/8 % mortgages. I have a small positive cash flow on these properties. My concern is that if we have a collapse and my tenants can't pay their rent, I may not be able to keep them. What are your thoughts about selling if I can and taking my losses instead of potentially losing everything? I am retired and bought the properties to try to provide an alternate cash flow to my pension and SS. If at all possible I would like Chris to weigh in. I realize that I must make my own decision but would appreciate some intelligent input to help me make that decision.