Ohio Rev. Code § 302.21
The board of county commissioners as provided in section 302.22 of the Revised Code may enter into an agreement with the legislative authority of any municipal corporation, township, port authority, water or sewer district, school district, library district, health district, park district, soil and water conservation district, water conservancy district, or other taxing district, or with the board of any other county, and such legislative authorities may enter into agreements with the board, whereby such board undertakes, and is authorized by the contracting subdivision, to exercise any power, perform any function, or render any service, in behalf of the contracting subdivision or its legislative authority, which such subdivision or legislative authority may exercise, perform, or render.
Upon the execution of such agreement and within the limitations prescribed by it, the board may exercise the same powers as the contracting subdivision possesses with respect to the performance of any function or the rendering of any service, which, by such agreement, it undertakes to perform or render, and all powers necessary or incidental thereto, as amply as such powers are possessed and exercised by the contracting subdivision directly. In the absence in such agreement of provisions determining by what officer, office, department, agency, or authority, the powers and duties of the board shall be exercised or performed, the board shall, within the limits of this section, determine and assign such powers and duties to any officer or officers of county government including the auditor, treasurer, engineer, recorder, coroner, sheriff, and prosecuting attorney. Any agreement authorized by this section shall not suspend the possession by a contracting subdivision of any power or function exercised or performed by the board in pursuance of such agreement. Nor shall the board, by virtue of any agreement entered into under this section, acquire any power to levy taxes within and in behalf of a contracting subdivision unless approved by a majority of the electors of the contracting subdivision.
The boards of county commissioners of any two or more counties may contract with each other or by contract create any joint agency to exercise any power, perform any function, or render any service which any board of county commissioners may exercise, perform, or render.
R.C. §302.21