No more than one sign advertising vacant land for sale or rent, not exceeding four square feet in area, may be placed on the property to be rented or sold. In the case of housing development projects, as a part of the Planning Board application, the developer may receive permission to maintain on his tract not more than two signs, limited to advertising his development, with the total area of each sign not exceeding 32 square feet. Such permit shall be issued by the Zoning Officer at the current rate for sign permits.