On the creation of such motor vehicle parking facility for the use of the general public, the city shall lease such facility to one or more operators to provide for the efficient operation of the facility. Such lease shall be let on a competitive basis and no lease shall run for a period in excess of four years; Provided, that leases of facilities in conjunction with office buildings, shopping centers, public facilities, or redevelopment areas may be for any period not to exceed twenty years. In granting any lease, the city shall retain such control of the facility as may be necessary to insure that the facility will be properly operated in the public interest and that the prices charged are reasonable. If the city is unable to secure a reasonable lease with another party for operation of the facility, the city may operate the facility itself. The provisions of sections 14-1731 to 14-1740 shall not be construed to authorize the city or the lessee of the facility to engage in the sale of any commodity, product, or service, or to engage in any business other than the purposes set forth in section 14-1732.