I did a MS that was coursework based part-time and worked doing research part-time, I was full time busy to get good grades.
I would recommend against full-time work with grad school. Some people in my MS program worked fulltime and took 2 classes a semester, and they really worked their butts off and were extremely tired all the time! Not that its bad to work that hard and save $$$ and prove you can manage your time, but realize that if you are getting and MS to improve you chances of admission, that grades in the classes are you #1 priority, so I wouldn't work more then part-time rather then risk my grades from being so worn out all the time.