I know this is a month old, but in the odd chance it comes up again. It's not that difficult to work in a 4 year program. A 3 year, probably more difficult, but most likely not impossible. I'm at USC and have worked since Spring of P1. During the school year I average 8-12 hours per week (more during P2) Over summer 1 I did the CVS summer internship (40 hrs/wk) and worked on campus on occasional Saturdays in between. Summer 2, I went from 2 kids to 3, started working as soon as my wife could get around the house comfortably, I went back to work again doing 20-30 hours per week (we're overstaffed). This summer I'll probably do the first summer rotation, take the 2nd one off to work and take a vacation, then finish 1 semester early to work and study for boards. Right now I'm averaging just under a B+ average. I should have all 1500 hours required to sit for boards even without the school hours.
Disclaimers: 1) My wife is a stay at home mom, so I don't have to worry about who's watching the kids while I'm at work. In a two income household this would be more of an issue. 2.) I'm living off student loans, and COA doesn't cover costs associated with a family, so my max loan amount is the same as a single person living away from home. Hence, I kind of have to work to make ends meet. Even so, I'm only making about 10-15K/year working.