I have a desktop PC at work, and a laptop at home.... or elsewhere.

What I want to do is use a USB HD to store my documents (about 130 Gb, maybe more). That would serve as backup and also port my files to my laptop. I'd like any of both computers to automatically sync all files there with local copies, so that I can work at either of them and keep updated copies of everything in both (plus the USB drive, which would allow me to work in other computers, too, apart from being another backup). Dropbox ins't a solution for me, due to pricing and 100Gb limit.

The workflow would be as follows, to clear things up:

1. I work on PC1. Changes in files are automatically synced to USB whenever a file is modified.
2. I go home and boot PC2. I plug the usb drive and local files are synced (if changed) with the most recent usb copies.
3. While I work at PC2, again, changes in files spread to my USB drive.
4. Whenever I go to PC1 again, I plug my usb and again everything synces.

So the questions would be:
a) Am I crazy?
b) Can it be done?
c) Will I have any file conflicts (provided I'm the only one that will modify the files)?