Foreclosed properties can be viewed by appointment, like any other property "on the market" . BUT chances are you will not be able to get the Listing agent to call you back for a showing, that is the agent/agency on the sign in the yard.
Call a Realtor in your area, and have him or her show you the property. Based on condition, comparables, and price you can make an informed decision. I had a buyer who purchased a move in condition foreclosure...those, however, you have to move on fast. Get your Realtor to start looking for props and alert you when they come up. They are vacant, so very easy to show.