I can not stress enough the pitfalls that others have outlined. You are buying a high risk "pig in a poke". The folks on the courthouse steps represent investors who can afford to "buy wrong" once in a while and absorb a $100,000 loss. Can you risk that?
Much better to find a Realtor you can work with to help you search for the REO's. Shoot me an email and I will send you current REO listings in whatever cities and price range you want, and set you up to get an email every day with new REO listings that meet your criteria .
One last word of warning. You will not find REO's at 50% of market value or anything near that. Most REOs will sell for 90-95% of a similar non-REO.
You can search for pre-foreclosures and foreclosed homes on my website.
If you do buy the first position, then you'll need to get ready for some legal action to evict the occupants. Get with a lawyer for that...
If you don't want to do trustee sale buying, then wait for the lender of the first to bring it to market with an REO agent. Depending on the condition of the property, the listing price will be priced lower than FMV for quick sale. If it's down right a dump, you may get a good price for the dump...get ready for fixing up and maybe get it up to code.
Lots to think about. I guess my question to you is, why do you want to buy a house, especially a foreclosed house?