It is highly likely you observed this on Trulia. It is a advertisement of deception. You already know "If it's too good to be true...." and this is no exception.
If you are serious about making a real estate purchase you should rely on serious tools. Real estate data appearing on Trulia and Zillow are for entertainment purposes for the sole purpose of selling advertising to real estate agents. If you are serious, promote yourself to serious tools such as REMAX.com or Realtor.com or ANY real estate professional website. Better still, pick up the phone and CALL a REALTOR to get plugged into the real database.
Best of success
Annette Lawrence, Broker/Associate