The Mayor and Councilmembers shall be qualified electors of the City and shall hold no other elected public office, nor any incompatible appointed public office, and shall have resided in the City for not less than two (2) years preceding the date of such election or appointment. If the Mayor or a Councilmember shall cease to possess any of these qualifications or should any of the conditions set forth in Section 15(D) and 16(C) of this Article exist, the office shall immediately become vacant. City employees are not eligible to stand for election or serve as Mayor or as members of the City Council. No person shall be eligible for the office of Mayor who shall not have attained the age of 25 years and no person shall be eligible for the Council who shall not have attained the age of 21 years.