The current reality is that many tax sale properties are bid down to 1%. If you are not the first 1% bidder, you may not win that property. As the redemption price is the same, the risk is that the tax sale will not be redeemed. One way to reduce risk is to buy the properties most likely to be redeemed. You can also minimize risk by buying more properties. This may allow losses on unredeemed properties to be offset by returns on redeemed properties and/or profits on properties to which you acquire title.