The Dallas Morning News has a story on a pretty ingenious scheme some scammers are using to collect rent; using foreclosed homes.
The scheme works like this: when a home is entering foreclosure, someone can appeal to have the process delayed, which, when used properly, gives the homeowner time to try to work out a financial deal. The scam starts during the period of hold-up on the foreclosure; that's when the scammers change door locks and rent out the property to, essentially, squatters.
But the scheme is easily disrupted by a real estate agent, or even the homeowners. To make sure your foreclosed property isn't being used by scammers, simply drive by.