The council may determine the annual salary of its members by ordinance; provided, that an ordinance establishing or increasing such salaries shall not become effective until the commencement date of the terms of two or more members elected at the next general election following the adoption of the ordinance, at which time it will become effective for all members whether or not they were elected in such election. The mayor and council members may also receive payment for actual expenses incurred in the performance of their official duties within limitations prescribed by ordinance.