We have had students work part time in the past but we do not recommend it at all.
It is really difficult to predict how much free time you will have during the week, and although we try not to overload the schedule there are the other course requirements and responsibilities which take up a fair amount of time.
In addition, you will need to identify if you are legally permitted to work part-time and as of when (period after your arrival) to ensure that you are not in breach of Swiss employment law. This varies from person to person depending on their nationality and student permit.
See also FAQ: What is the schedule like?