Cal. Government Code § 37443

In any sale or lease of property with option to purchase, made or entered into pursuant to Section 37442, the purchase price for any property sold or the consideration for or rentals payable pursuant to any lease shall be payable at such times and in such amounts as the legislative body may determine. In any sale or lease of such property with option to purchase, the legislative body may provide that all or any part of the unpaid portion of the purchase price shall be secured by a mortgage or deed of trust. Where such property is leased with an option to purchase, the legislative body may provide that all or any portion of the consideration paid for or rentals received by the city under said lease may be credited against the purchase price specified therein. Any sale or lease of such property with option to purchase shall be made subject to any duty or obligation imposed by law or contract upon the city with respect to such property. Any sale of such property shall be made subject to the requirement that the purchaser use the property, or allow the use of such property, as a public airport for not less than 10 years from the date of the sale unless earlier discontinuance of such use is permitted by the Administrator of the Civil Aeronautics Administration of the United States Department of Commerce.