N.J. Stat. § 40:48-5: Private contracts generally

When, under any provision of this subtitle, any municipality is authorized to render any service to the public, it may, in lieu of providing and maintaining the equipment necessary for rendering such service at its own expense, contract with any person to render such service on behalf of the municipality, under its control and direction. No such contract shall be let until specifications showing in detail the service to be rendered shall be prepared and rules and regulations governing the same shall be adopted. The contract shall be let, after due advertisement, to the lowest responsible bidder, who shall give ample security for its proper performance.