The sheriff or the state‘s attorney, or both, of an adjoining county may run for election in a county which has adopted the county consolidated office form of government. Any such officer of an adjoining county so elected shall serve for a term of four years and until that officer’s successor is elected and qualified. An officer elected under this section is eligible to serve in such dual capacity and must receive, in addition to the salary as an officer of the county of residence, a sum not exceeding one-half of such salary, to be fixed by the board of county commissioners. The additional salary must be paid by the county in the same manner as other county officers are paid.