PROBLEM TO BE SOLVED : To provide a real estate lease article transaction system capable of making efficient and fair transactions in view of the balance between demand and supply.SOLUTION : Information about properties to be vacated in the future is posted on a Web site which an information provider 130 is operating, along with information about currently vacant properties. If a customer-reserved property that is to be vacated is deemed to be ' currently vacant' before the desired move-in date, then the information provider 130 reports this to the customer 110.