The chief executive officer of a city under the city manager plan of government shall be a city manager, who shall be responsible for the proper administration of all affairs of the city. He or she shall be chosen by the city council for an indefinite period, solely on the basis of administrative qualifications, and need not be a resident of the city or state when appointed. He or she shall hold office at the pleasure of the city council and receive such salary as the city council shall fix by ordinance. During the absence or disability of the city manager, the city council shall designate some properly qualified person to perform the duties of the city manager.