The mayor and each commissioner shall have an office at the municipal building or rooms, and shall devote such time to the duties of their respective offices as a faithful discharge thereof may require.
The total and only compensation of the mayor for the performance of his duties shall be an annual salary, which shall be established by the council prior to the mayoral election. The total and only compensation of each commissioner for the performance of his duties shall be an annual salary which shall be established by the council prior to the election in which commissioners are elected. An increase or decrease in the salary of any such official shall not take effect during the term for which he is elected.
65 ILCS 5/4-6-1