Where property is listed with real estate broker for sale for a stated amount, which included an existing mortgage, the commission, unless for some special reason to the contrary, should be based on a sale for this amount; but where, in order to promote the sale, money for improving the properties is raised by a mortgage, executed by the owner and guaranteed by the buyer, who assumes its payment, the commission should not be increased on that account, unless an agreement to that effect may be implied from other circumstances. Fuller v. Preston, 191 P. 493, - Kan. Sup. - .