Redundancy for 2-3TB of data per month

So I work for a company that does all of the graphics in house. We make our own videos, product pictures, packaging, you name it. We are looking into a solution for redundancy.

Currently our video guy just buys 2 drives a month and puts the data on both and throws them in a box. The problem with this if there was ever a fire we would be out all of that data. We have two offices and would like to have a solution to sync data between the two so nothing is ever lost. The main issue we have is storage.. It's expensive. We are trying to find a nice low cost solution to store 2-3 TB of data per month with redundancy.

We need a nice way to have an expandable network. We always want to be able to go back and fetch old files. We don't need redundancy at our corporate office, just our backup office.

I'm curious if any of you guys have had to deal with this before. The only solution I can think of is having a machine per year that has all of the storage space we will need and just duplicate that setup per year and have a master node that pulls from each one. I really haven't done anything on this magnitude so this is the only solution I can think of.

The company I work for is a fairly small one (only around 40 or so employees).

Any suggestions or tips are greatly appreciated.