To make a saving in terms of space and time and to improve the quality of previous arrangement/negotiation by using a virtual previous arrangement space (virtual business office) in the planning/building of custom-built house.

In this system such that a previous arrangement/negotiation site manager (housing maker) device is made as a base point, the virtual previous arrangement space between the device and a customer/business collaboration side device is constructed, and the previous arrangement/business negotiation for housing related information are performed, the customer/business collaboration side device sets conditions necessary for the previous arrangement for the housing related information, and the site manager side device constructs the virtual previous arrangement space depending on the set conditions, generates desired previous arrangement information necessary for the previous arrangement for the housing related information, and stores generated previous arrangement information at each previous arrangement as needed.