The lawful use of land or buildings existing at the time of the passage of this Chapter, although such does not conform to the regulations, may be continued. A non-conforming building, structure or portion thereof which is or hereafter becomes vacant and remains unoccupied or, in the case of use of land, ceases such use for a continuous period of six (6) months shall not thereafter be occupied or used except by the uses which conform to the use regulations of the district in which it is located. In those instances where non-conformity of use, land, or building exists, clear intent upon the part of the owner to abandon the non-conformity or non-conformities shall thereafter render the said property to the use regulations of the district in which it is located.