In Hasage v. Philadelphia Zoning Board of Adjustment, 415 Pa. 31, 202 A.2d 61 (1964) our Supreme Court held that a landowner is duty-bound to check the zoning status of a property prior to purchase. Where a landowner fails to review the relevant zoning ordinance before purchasing a property, he may not advance the resulting ignorance in support of a variance by estoppel. Id.