Judges of the supreme court and of the court of appeals shall have been citizens of the United States for at least fifteen years, and qualified voters of the state for nine years next preceding their selection. Such judges shall be at least thirty years of age. Except as provided by section 6, judges of the court of appeals shall be residents of the court of appeals district in which they serve. Circuit judges shall have been citizens of the United States for at least ten years, and qualified voters of this state three years next preceding their selection, and be not less than thirty years of age and residents of the circuit for at least one year. Associate circuit judges shall be qualified voters of this state and residents of the county, at least twenty-five years old, and have such other qualifications as may be provided by law. Every supreme, appellate, circuit, and associate circuit court judge shall be licensed to practice law in this state.