Nadine, when a home owner gets behind on his mortgage payments, a bank may start foreclosure proceedings. This starts with a 'notice of default' and then later they can schedule it for a foreclosure auction. When these notices go out, sites like RealtyTrac will pickup them up and list the home on their web sites.
While this is going on, the home owner is often negotiating with the bank to keep their home. If they are able to make back payments, then the foreclosure auction will be stopped. Later, if they get behind again, they'll get another notice. If a homeowner can negotiate a loan modification, then that would stop the foreclosure process. This back and forth can go on for months... or longer. Because of this, none of these pre-foreclosure sites have complete, accurate and timely data.
Also, and more important, many home buyers think they can contact a bank for a pre-foreclosure and purchase a distress property. You cannot. The homeowner is still the owner and is the only party who can approve the transfer of title to another party. If the homeowner doesn't want to sell, you cannot buy it. Period. If he does want to sell, then you negotiate a contract with the homeowner, and then the bank must approve the contract as a short sale. Then, you go to closing and buy the property from the homeowner - not the bank.
There's three ways to find and buy a distress sale: 1. short-sales listed in the MLS, 2. buy at foreclosure auction, and 3. buy from the bank after they complete a foreclosure.
I hope that helps. Sites like RealtyTrac lead home buyers to believe there is a secret market to buy distress homes when there really isn't.