You can work up to 20 hours per week. Working more than 20 hours per week is a violation of your study permit conditions. You can lose your student status for doing this, and may not be approved for a study or work permit in the future. You may also have to leave the country. You may be eligible to work in Canada while studying, if your study permit includes a condition that says you can work on or off campus. You must also meet all the other requirements. You can only start working in Canada when you start your study program. You can't work before your studies begin.