If you're looking at a Short Sale or a RealtyTrac listing it may not be possible to buy it for the price listed.
You see the RealtyTrac listings are just notices of foreclosure paperwork filed at the courthouse. If a Home Equity Line of Credit files a foreclosure, there still may be a first mortgage for $500k.
It's not possible to buy a $200k property for $100k. You may be able to get it for $150k if you buy it at the courthouse foreclosure auction for ALL CASH the same day, though. You will have to do a lot of homework to verify what liens will survive the foreclosure and you buy it "as is" and without title insurance. So don't make any improvements because there are a lot of faulty foreclosures and some owners may try to get their house back!
PS A South Miami Realtor can give you access to the "real" prices.