You’re paying for the 1st right of that property, the tax sale is just the lien that’s been placed on the property, if it has an mortgage, the taxes do not override the mortgage owed, if it’s a foreclosure the bank still is owed. Paying a few 1,000s does not give you immediate rights to the house. This sale is held by the County, generally once each year. What is purchased by the winning bidder is not the deed to a property. The purchaser’s money pays the delinquent taxes to the County on behalf of the delinquent property owner. In exchange, the purchaser is given first lien position on title, ahead of mortgages (sometimes), deeds of trust, and judgments, subordinate only to State tax liens. Check out for all of your Washington, DC Area Real Estate Needs!