If it is in tax sale, they at least know the address and the owner of the property. If the owner doesn't live at that address, they have got to have a mailing address of where the tax bill goes (at least I would hope so).

If the owners are deceased, that is another whole ball of wax. Of course, I am only familiar with how the counties I cover in Maryland work. I don't particularly like to mess with tax sales here in Maryland. The owner has 18 months to redeem the property, pay the back taxes and any attorney fees.