The council shall not create, audit, allow or permit to accrue any debt or liability in excess of the available money in the treasury that may be legally apportioned and appropriated for such purpose, except in the manner provided in this Charter, for incurring indebtedness. No warrant shall be drawn or evidence of indebtedness be issued unless there is at the time sufficient money in the treasury legally applicable to the payment of the same, except as in this Charter provided.