Section 59. The selectmen and all boards, committees, heads of departments, or other officers of a town authorized by law to expend money shall furnish to the town accountant, or, if there is no town accountant, to the appropriation, advisory or finance committee, if any, otherwise to the selectmen, not less than ten days before the end of the calendar year, or not less than ninety days prior to the date of the start of the annual town meeting, whichever is later, detailed estimates of the amount necessary for the proper maintenance of the departments under their jurisdiction for the ensuing fiscal year, with explanatory statements as to any changes from the amounts appropriated for the same purposes in the then current fiscal year, and an estimate of amounts necessary for outlays or permanent improvements. They shall also prepare estimates of any income likely to be received by the town during the ensuing fiscal year in connection with the town's business or property intrusted to their care. The selectmen shall include in their estimates the salaries and expenses connected with their own office, and the salaries of all other town officers shall be included in the estimates for the office, department or branch of the public service of which they are in charge. The treasurer shall, in addition to his estimate of the amount required for the maintenance of his own office, prepare a separate statement indicating the amounts required for the payment of interest on the town debt and for the payment of such portions of the town debt as may become due during the ensuing fiscal year.