It shall be the duty of the purchaser or purchasers at treasurer's sale, as soon as the property is struck down, to pay the amount of the purchase money, or such part thereof as shall be necessary to pay off the taxes and costs, as also one dollar for the use of the prothonotary for entering the acknowledgment of the deed; and in case the amount is not forthwith paid, after the property is struck down, the sale may be avoided, and the property immediately set up again by the treasurer; and it shall be discretionary with the commissioners of the respective counties, what lands they will purchase in for the use of the county.
72 P.S. § 5912