The corporation shall have a board of directors in which all powers of the corporation shall be vested and which shall consist of not less than three nor more than nine directors, all of whom shall be duly qualified electors of the municipality or county in which the corporation was formed. Decisions of the board of directors shall be by majority vote. The directors shall serve without compensation except that they shall be reimbursed for their actual expenses incurred in the performance of their duties. No director shall be an officer or employee of the authorizing municipality or county. The initial directors shall be elected by the incorporators of the corporation. Directors shall hold office for overlapping terms. At the time of the election of the first board of directors the directors shall be divided into three groups containing as nearly equal numbers as possible. The first term of the directors included in the first group shall be two years, the first term of the directors included in the second group shall be four years, the first term of the directors included in the third group shall be six years. The terms of all directors thereafter shall be six years. The directors shall elect their successors and fill vacancies in the board of directors, subject to the approval of the governing body of the authorizing county or municipality.