PROBLEM TO BE SOLVED : To provide a building property free observation system by which even a customer who is not familiar with the geography of the area easily visits the location of a property without a property guide and light-heartedly observes the inside of the property by himself or herself till he or she is satisfied.SOLUTION : When the customer 2 is introduced an apartment 3 for rent by real estate agent 1, the customer 2 visits and observes the apartment 3 by himself or herself without the guide. In this case, handy navigator 4, a duplicate key 5 and a compass 8, etc., are lent to the customer 2 from the agent 1. The location of the apartment 3 (a course), a house rent, the agreement of rooms and an outer appearance drawing, etc., are displayed in the screen of the navigator 4 and the map screen is magnified or reduced as necessary. A copying action is easily discovered when the action is performed by attaching a cap for preventing copying to the duplicate key 5.