(1) It is the duty of the governing board of every municipal corporation to have a thorough audit of the financial affairs of the corporation, including all receipts from every source and every expenditure or disbursement of the money of the corporation, made by a disinterested person skilled in such work, as often as every two (2) years.
(2) Each audit shall cover the period extending back to the date of the last preceding audit.
(3) The cost of each audit shall be paid out of the funds of the municipality, and a sufficient sum shall be appropriated by the board for that purpose.