Methods and systems for electronic commerce are provided in which a buyer requests a merchandise estimate by selecting estimate items registered by a seller, selects one of various estimates suggested by the seller in response to the request, and performs payment for the merchandise. One method for providing electronic commerce includes receiving, from a buyer terminal, an estimate request selecting at least one of a plurality of items from estimate request information registered by a seller terminal, providing at least one estimate to a buyer according to an estimate response from the seller terminal, and receiving an estimate rejection or a purchase request in response to the at least one estimate from the buyer terminal and performing a corresponding process.