As many as are available, and that will depend on the job you land.  Our Career Site typically includes openings with part-time and full-time schedules.  Some companies may let you choose your shift/hours, taking on extra hours if desired, while others will require a set schedule.  The specifics for each role will be listed in the job description.

At a minimum, you should expect to work at least 20 hours a week - it is rare that an opening is available that requires less than this.  The more flexible you can be, the better your odds of landing a job.