Probably not a lot because you won't have a lot of time. I make a couple of hundred dollars a month from my job that I have. I work 4 hours a week and that is the max I can handle. So I wouldn't plan on any more than that.
Federal work study jobs at SCO pay anywhere from $11-15 an hour. $11 for the jobs where you sit and study (like the library) and $15 if you work more than study, like tutoring. I'm assuming the dollar amounts are very similar to this at other schools.
We talked a lot about this at my interview. If you work at ICO and have a job that doesn't let you study during your job you make like $9-10/hr. If you have a job that allows you to study while working you can make $8/hr. Most students only work 5-8 hours a week because the schedule is so demanding. Although if you get a bunch of jobs that allow you to study you could easily pull off more hours. It also depends on how much you can handle.