Working full-time and going to school full-time is like having two full-time jobs--one that pays you, and one that you pay for the privilege of attending. I tried one semester of a full-time job while attending school full-time, and I now have to spend an extra YEAR at school to make up for the grade drops. If you can get away with working a part-time job, then do it.
Maybe you can do both and keep your grades up without going insane, but if you HAVE to work full-time to pay for school and room and board, then it might be best to take the minimum amount of credits required to maintain full-time status. I know that at my school it is about 12. If I had the chance to go back a few years, I would work full-time and take 12 credits instead of 18. It was a very silly thing for me to attempt, especially because (among other things) I have atrocious time-management skills.
As distasteful as the idea of a roommate or two sounds (and I have yet to have a roommate for that very reason), it does cut down on the cost of an apartment. I have a coworker who rents a nice, two-bedroom apartment with three roommates, each one pays $115/month plus a portion of the utility, cable, and electric bills. (When I was at school on my own, I paid $500/month for my own space in a dorm...an extravagence I was unable to reasonably afford.)
Most universities always have openings for jobs. Mine has a whole board for off-campus and on-campus job openings, and the board is updated quite frequently.
I really wouldn't recommend going to school full-time while holding down a full-time job. Going to school really requires a lot of work--a lot more work than high school ever prepares you for--and when you add up all the study time, class time, and time spent on various projects, it comes out even with or, sometimes(like during Finals), greater than the 32-40 hours a week a full-time job entails.
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