in the premises so demised to and with any lesee or lessees thereof at any period during the term granted or agreed for by any lease or contract made by him and for him the said Donald McLean to execute any lease or leases contracts or agreements for granting any leases and with or without power to purchase the freehold or inheritance of the said lands or any part or parts thereof and also to give discharges for any rent or rents now due or that may hereafter become due for the same and for any purchase money or other monies or damages which have become due or may become payable to the said Donald McLean and also upon non payment of any rents which may be now