Unless prohibited by this Chapter, two temporary on-site real estate signs, each not exceeding six (6) square feet in area, and less than six (6) feet in height that advertises the sale, lease or rental of a structure or land. The sign shall be removed within seven (7) working days following the sale, lease or rental of the property. Open house signs shall be removed within a twenty-four (24) hour period following the conclusion of the open house.