When any assessment has been completed the secretary shall immediately notify each member by mail directed to the member’s last known address of the purpose and amount of such assessment and of the member’s share thereof, and the person to whom and the time when such payment must be made, which shall not be less than 30, nor more than 90, days thereafter; and such person, if the bylaws so provide, may collect a commission of not more than two percent of each amount in addition thereto.