The agency or entity provided by the agreement to administer or execute the agreement may be one or more of the parties to the agreement or a commission or board constituted pursuant to the agreement or a person, firm or corporation, including a nonprofit corporation, designated in the agreement. One or more of the parties may agree to provide all or a portion of the services to the other parties in the manner provided in the agreement. The parties may provide for the mutual exchange of services without payment of any consideration other than such services.