(a) All governmental units within the boundaries of a region which are parties to the agreement for the establishment of a regional planning and development commission shall be represented on the commission as provided in this section. The agreement may provide formulas and procedures under which smaller governmental units may select a common representative and larger units may select more than one representative, but there shall be at least one representative for each county and for each city of over 10,000 population. At least a majority of the representation of a commission shall be elected public officials of the participating governmental units. This section shall not apply to any counties which have formed any regional planning commissions.
(b) The terms and manner of selection and replacement of the commission representatives shall be specified in the agreement or, pursuant to the terms of the agreement, by ordinances or resolutions adopted by participating governmental units. Terms of representatives who are not elected officials shall be arranged to provide overlapping periods of service. The term of any representative serving in such capacity by virtue of elective public office shall expire with his incumbency in such office.
(c) The agreement shall include the formula by which participating governments will contribute to the financing of the commission and the procedure for amendment, for addition of other governmental units within the region which are not parties to the original agreement and for withdrawal from the agreement by a governmental unit and for dissolution of the commission.
(d) Any governmental unit included within the boundaries of a region but not a party to the agreement and petition shall not be represented on the commission nor be entitled as a matter of right to services provided by the commission until it joins the commission by appropriate official action as provided for in the agreement or the bylaws of the commission.