Is there a customized realtor sales and contact management system in civi
CiviCRM can be customized by developers and implementers to suit a wide variety of needs. It may or may not do what you need out of the box, but one of the CiviCRM Partner companies could help you out.  

CiviCRM is the best open source CRM going and when used with a CMS like Drupal can be quite extensible and powerful.