I did 35 to 40 hours a week my first year in pharmacy school. It's possible, but be prepared to be envious of the people in your class who aren't working. You won't have much free time, and scheduling can get tricky at times. If you're good at scheduling, that will help immensely.
It can also be tricky with last minute studying, since the time isn't there. Try working after pulling an all nighter...I can't do it. If you can, kudos to you.
If you have a low stress job, or one where they don't mind you studying while you're there, that would be ideal. I've heard of people working at a hotel front desk overnight, and having lots of free time to study while they're there.