Pre-Foreclosure
  
Ooh, this is bad. You don't want this.
When something is like..."pre-death," or "pre-beheading," or "pre-bankruptcy"...it ain't good, no matter what it is. So if a home is pre-foreclosure, it means that it's likely almost past the 90 days with endless lawyer notes and filings before the sheriff comes and forcibly removes the crying spouse and children, so that the bank can sell the home to someone else.
If you see a pre-foreclosure sign on a house, it may be worth taking a look. Banks jsut want to sell those things as fast as possible, and really just want to get their loan money back. So they'll often drop the price meaningfully to get rid of the thing.
Bid low. Stay tough. Ignore the family living in the station wagon parked curbside.