(1) If a house is unoccupied, a notice issued under section 7 may require the owner to give possession of the same to the ¹[Officer Commanding the station] within twenty-one days from the service of the notice.
     (2) If a house is occupied, a notice issued under section 7 shall not require its vacation in less than thirty days from the service of the notice.
     (3) Where a notice has been issued under section 7 and the house has been vacated in pursuance thereof, the lease shall be deemed to have commenced on the date on which the house was so vacated.