I think you are looking at posts from a site called Realty Trac. Those homes are, indeed, foreclosed or in pre-foreclosure status. However, they may not be available for purchase and the 'price' you see is not the asking price, it is the amount that was owed to some bank at the time the bank either foreclosed on the home or began the foreclosure process. Some of these homes have multiple mortgages and/or liens filed against them so, if you are seeing a second or third mortgage the amount may be very, very small. It's very misleading.
If you want to purchase foreclosed properties or properties in pre-foreclosure status, find a good local realtor with experience in these types of transactions and work closely with that agent. The ONLY way for a consumer to purchase one of these properties is when the owner, whether it be the bank or the current owner and mortgagee, decides to list it for sale with an agent. And those are the facts, plain and simple.