On such date in each year as shall be fixed by the Council, the City Manager shall send to the Council a careful estimate, in writing, of the amounts, specifying in detail the objects thereof required for the business and proper conduct of the various departments, offices, Boards and Commissions of the City, over which the office has control, during the next ensuing year. The City Manager shall also at said time submit to the Council an estimate of the amount of income from all sources of revenue, exclusive of taxes upon property, and the probable amount required to be levied and raised by taxation.