I have a lot of experience creating applications that tie into outside web services, and using maps that allow the user to click on locations and see further details. I would think that the best approach would be to use a custom app, loaded into the user's device, that connect to an online database. The application would allow the user to upload pictures and other information about the property, organize it by location, and allow relevant information to be searched both from the internal database, as well as outside services, such as the tax rolls. Using a custom app, as opposed to a strictly web interface, would allow for device level authentication, so that only that user, on that device, can access their information. Of course, you would also want an administrative program set up, to assign and replace devices, add users, and change individual user's permissions. Let me know if you would like to discuss further.
Thank you,
Chris Howell
etherVision, inc,