[Problem] in buying real estate, seller' s surface by, for each of those two agent from being interposed to the buyer, the buyer is searching property, apartment application, even if the manufacturer must be passed through all the questions, the seller can flexibly change their prices, questions, cannot be complemented with property information, the buyer seller party in the communication cost is high, and, is applied to solve consensus transaction until the time for. [Solution] the membership registration, the advertisement placement of auxiliary item is sold, the selling item retrieved, can be provided on the Internet site for communication messages (Figure 1 1 a) to develop the function of the platform and providing [...] real estate. Each of the sellers and buyers computer terminal, trading can be consensus smooth, even real estate business cost can be suppressed. Figure 1 [drawing]