When I went to the financial aid office, I was told that they actually assume, no matter what, that each student works a full-time job over the summer. This must be the $4400 mentioned previously. There is an appeal you can do to cancel this: you must apply, and have proof of rejection for, 10 different full-time jobs. I actually tried to do this, got rejected by at least 20 places, but there are few employers willing to give out their contact information for proof. My advice: get a summer job, even part-time if you can (kinda late now..)
As for jobs during the school year: as far as qualification goes, I heard at my very recent mission2mac that you must have applied for OSAP to be eligible to apply for work programs. It doesn't matter if you received any OSAP, though.
I know that I will definitely try for a job on campus. Personally, I find it hard to imagine
not working. They don't give you many hours (8 - 10 hours per week), and a little extra cash is never a bad thing, especially if it goes towards lessening the imminent loan of doom and destruction.
So yeah, I think you should go for a job, just don't take the ones I want!
(<---me)