The commission shall have charge of the erection of new buildings and the substantial alteration or enlargement of existing buildings, used or to be used by the state or any of its departments or agencies for office purposes in the city of Trenton, but shall not incur any debt or obligations therefor until the proposed new building, alteration or enlargement work has been submitted to the legislature with the estimated cost thereof and such other detail as may fully inform the legislature as to the proposed erection, alteration or enlargement, and the improvement is concurred in by both houses of the legislature.