In areas where some lots are developed with a front yard that is less than the minimum required for the district by this Zoning Ordinance, or where some lots have been developed with a front yard greater than required by this Zoning Ordinance, the following rule shall apply. The front yard depth for a principal building located on a lot within 250 feet, measured along the street line, from the nearest corner of the lot under consideration to any portion of two or more lots in the same block, and which lots are occupied by dwellings that front on the same street as the proposed principal dwelling, shall be the average front yard depth of such existing dwellings.

   1.   Buildings located entirely on the rear half of a lot shall not be counted.

   2.   Buildings shall not be required to have a front yard greater than 50 feet or less than that required in the zoning district in which they are located.

   3.   If no building exists on one side of a lot within 250 feet of the lot in question, the minimum front yard shall be the same as the building on the other side.