There are so many counties in the United States that conduct separate tax sales for their own liens. Why do these counties sell these tax liens in the first place? It is because they need the money to pay for public services such as police, schools, hospitals, parks, and many more. By state laws, every county is authorized to collect the taxes due from each homeowner, which remains unpaid by selling at public auctions. This can either be tax lien certificates or tax deeds. It can also be both.
There are some books on the subject of selling tax liens. Most counties have websites where you can get a list of these liens for sale. Auction dates and frequently asked questions are also available to read. Moreover, there are a number of approaches you can take to get more information which can be found in the internet.