Backup/Time Machine solution for an office full of iMacs?
You can simply put an Apple Time Capsule in your network and select this as Time Machine backup volume. And you may choose an encrypted backup to ensure more privacy. This works perfect in my office with a dozen MacBooks.

A more cost efficient solution may be a 3rd party solution like a Synology DiskStation containing a Raid 1or 5. Synology also offers Time Machine support which works seamless for me at home.