Except pursuant to a purchase agreement with the tenant for the purchase of his dwelling unit or the space or lot in a mobile manufactured home park on which his dwelling unit sits, any provision in a tenant’s lease that allows a landlord or declarant at his option, on conversion of a building or mobile manufactured home park to a common interest community, to cancel and terminate such contract or lease without conforming to the requirements of sections 47-282 to 47-293, inclusive, is unenforceable and contrary to public policy.