It is possible to physically partition your drive, and install a different copy of OS X on each partition. You can use the startup disk preference to pick which one you use.
Or an easier solution (and one that's less wasteful of disk space):
Why not just make another user, one just for work? You can easily switch between without logging out, and you don't need to waste a bunch of space by installing OS X again.
As far as the virtualization goes, it's probably technically a violation of the license to run multiple copies simultaneously unless you own multiple copies of the OS.