Work-study jobs are paid for (mostly) by the government. The college pays something like 25 cents an hour, or perhaps even less. You receive the money like you were working a regular job.
Having a job on campus is very convenient, too.
Work study jobs, at least in my experience, have flexible hours - a few hours here and there between classes. So if you've got 3hrs space between classes, go work during that time. Then more classes, then maybe more work, then go home and do homework.
Some work-study jobs also have lots of downtime, during which you can do homework.