I held a couple of different work-study positions over my first two years of medical school. Starting the summer before first year, I did some research in the ENT department - I really wanted to continue throughout my first year, but the amount of time demanded by school and other extracurricular activities was too much, and thus my project(s) fell by the wayside. A more organized student, one who participated in fewer extracurriculars, or one who didn't mind surrenduring every last possible shred of a social life might have been able to balance things better than I, but until you know how you need to study in med school, I'd advise you to be careful what you commit to during your first year.
Second year, I was able to make some money through the Office of Medical Education (OME) as a tutor. A couple of other second-years and I tutored first-year students in some of their classes. You could work as much or as little as you wanted. The pay wasn't fantastic (I don't remember exactly, maybe $10-12/hour? Don't quote me on that, it may have been less/more), but it was something. In order to get that position, however, I believe you have to be selected by the OME. I thought it was worthwhile, and it is something you can put on your CV.
I second LS's opinion that it is more worthwhile to serve in a research position than in an administrative position. Tutoring was all well and good, but I didn't get a paper, abstract, or poster out of it. If you're going to spend your time trying to make money, at least with a research project you have the potential to get published. If I had it all to do over again (hindsight being 20/20 and all), I would have found a relatively flexible basic/clinical science research project the summer before 1st year, and stuck with it through all 4 years. You'll have a lot of time in the summer between 1st and 2nd year, and again during 4th year, to really crank out a lot of quality data. And then you'll have something to present at the Medical Student Research Day.
