Through the facility of multiple listing, information concerning individual listings can be made known to all REALTORS® who participate in the activity. In associations of REALTORS® with few members, the actual operation can be very simple. Each REALTORS® can duplicate enough copies of the information concerning his listing to distribute to all other participants. However, when many REALTORS® are involved, the distribution of information becomes more burdensome and may require reasonable rules of procedure and efficient central office management to expedite the service. Regardless of the method, however, the basis of the multiple listing activity is the creation of a facility whereby REALTORS® may most effectively invite other brokers to enter into cooperative agreements with them for the sale of their listings and provide information necessary to permit such cooperation; by which information is accumulated and disseminated to enable authorized participants to prepare appraisals and other valuations of real property; and by which participants engaging in real estate appraisal contribute to common databases.