As used in sections 376.291 to 376.307, the following terms mean:
As to a mortgage on a leasehold estate, real estate shall include the leasehold estate only if it has an unexpired term, including renewal options exercisable at the option of the lessee extending beyond the scheduled maturity date of the obligation that is secured by a mortgage on a leasehold estate by a period equal to at least twenty percent of the original term of the obligation or ten years, whichever is greater;
§ 376.292, RSMo