Why are houses with unpaid property taxes a unique opportunity? One simple reason, they are almost never impeded by mortgages. The reason is that if the property was mortgaged, the mortgage company would most certainly pay off the property taxes in order to avoid losing the property at tax sales and because most mortgage payments include property taxes. Another reason is that taxes may not have been paid for a long period. Most states dictate how long a property can last without taxes being paid, however the county can extend this period at their discretion. Therefore the reason property taxes are not paid is probably, among other reasons, that the owner of the property does not have enough funds.
Properties with unpaid property taxes are a lucrative investment opportunity and therefore purchasing such a property at a tax auction may not be ideal, due to the heavy competition to acquire the property at the auction. However, if you spend some time looking for such properties, contacting the owners direct would result in much lesser price than the property is worth. More often than not these owners aren’t interested in the property so they will sell it at a token price. Acquiring the property direct from the owners will result in a unique and profitable investment.