...and store the DB file on the local shared drive without a problem
Actually, that IS a problem and one that can damage your database file very easily.
You can find product specification data that lists the hardware/software requirements for server in the knowledge base. There are also additional articales besides the one above you can find if you specify "sharing" in you keyword search. You'll find a link to the knowledge base at the top of this screen.
You may want to consider contracting with a fileMaker hosting service to host your database so that all can access the DB over the internet using either a web browser (if you set up your database to work with Instant Web Publishing) or from FileMaker Pro clients.