All applications to lease any real property for the purposes of the city or any of the counties therein, including the premises required in accordance with law for armories and drill rooms and places of deposit for the safekeeping of arms, uniforms, equipment, accoutrements and camp equipage of the national guard, must be presented to and passed upon by the board of estimate. The board, upon the report of the commissioner of general services, and upon such further inquiry as such board, in its discretion, may make, may authorize a lease of such premises as shall be specified in its resolution, at the rent therein set forth for a period not exceeding twenty-one years. Such lease may contain a provision for renewals thereof at the option of the city. Such lease, however, shall not be authorized except at a fair and reasonable rent, and unless the board is satisfied, and shall so express, that it would be for the interest of the city that a lease of the premises for the purposes specified should be made. If the city, prior to the making of the lease, shall have entered upon the possession of the property, the lease may be made to commence as of the date when the occupation commenced.