You should already have some backup strategy.. particularly in a work location.
Mixing files and TM backups particularly for 5 computers on a TC is not great.. but you can add a USB drive for the shared files..
See pondini on mixing backups and data on the TC.
Q3 here.
http://pondini.org/TM/Time_Capsule.html
As a file server or NAS.. the TC has one big flaw.. it has no way to back itself up. And Time Machine cannot backup network drives. So if the files stored on the TC are corrupted (always a possible event with wireless from multiple clients in use).. do you have a simple backup method to keep the files on the TC safe.