That might be overkill unless you need all that storage space. Just how big are the "Common" files?
I have a similar situation and run my business from home where I have several computers and a laptop. I keep all my business files on the laptop and back up the entire system to a 250 Gb external hard drive using Acronis True Image. All my essential business files including database, spreadsheets and documents will actually fit on a 1gb encrypted memory stick so I carry that on my key ring.
I also leave a copy of all my business documents on a second computer at home which is wireless networked. The only problem with this is that I have to remember to synchronise the files and keep them updated with the latest version. It takes less than 10 minutes to do this on all the media I use.