In a side yard only in cases where a variance pursuant to N.J.S.A. 40:55D-70(d) is granted by the Board of Adjustment; provided, however, that if parked in a side yard the limitations set forth in paragraph 2a, b and c above concerning rear yards shall also apply; provided further, however, that in the case of a corner lot no portion of the recreational vehicle or the screening provided therefor shall be closer to the street than the setback requirements of this chapter for principal buildings.