It's possible to work as a student in Belgium. However, there are limits on how many hours per week you can work. Also, due to the workload required for you to be successful in your studies, financing your education through a student job is not advisable.
For details about working as a student, check the Study in Flanders website, where you will find a nice overview of the limitations on and requirements for student work. You will some extra information in our student portal.