Answer: Nine years.
Step-by-step explanation:
According to the Constitutional Qualifications of a Senator of any state in the United States of America, a candidate must be of thirty years of age at the time of election. They must also have been a resident citizen of the United States for no less than nine years and must not be an inhabitant of the state the candidate stands to represent over a given period of time. These were the three main rules established by the delegates of the time in the 1787 Constitutional Convention for membership to the House and Senate.