A geographic farm means that you have a mailing address for these people. If you don't have a name, the value of this database is minimal and probably should be deleted. If you would like to determine who has moved, use your Real Estate CRM to print mailing labels for these people and send them a postcard. Make sure to use a First-Class stamp and include the directive "Return Service Requested" on your mailing label. Your Real Estate CRM can include this directive on your mailing label for you. When you do this, the Postal Service will return any postcards for recipients who have moved. Use the local tax records to look up who the current owner of the home is and update your database. This also allows you to determine if the person living in the home is the owner, or a renter as well.