Whenever governmental agencies or municipalities desire to act under the provisions of this chapter, the relationship established between them shall be fixed by contract. Such contracts may be made by governmental agencies and municipalities under the provisions of this chapter in the manner and to the extent that natural persons may make contracts for like purposes, subject only to the limitations provided by this chapter. Such contracts, before becoming operative, shall be approved by a vote of the majority of the members of each of the respective governing bodies of the municipalities or governmental agencies operating under the provisions of this chapter. If any municipality desires to act under the provisions of this chapter without establishing a relationship with another municipality or agency, it may proceed as a separate and independent enterprise.