(1) A board of county commissioners shall be elected in each county at the general elections as provided by section 31-703, Idaho Code.
(2) No person shall be elected to the board of county commissioners unless he has attained the age of twenty-one (21) years at the time of the election, is a citizen of the United States, and shall have resided in the county one (1) year next preceding his election and in the district which he represents for a period of ninety (90) days next preceding the primary election.
(3) Each candidate shall file his declaration of candidacy with the county clerk.
(4) Each candidate who files a declaration of candidacy shall at the same time pay a filing fee of forty dollars ($40.00) which shall be deposited in the county treasury.