If you have already been granted a student visa for Switzerland you are permitted to take up a part time job whilst studying. However, you are not allowed to work more than 15 hours per week.
With regards to how much you can earn, this will depend on your skills and background. If you are studying finance or IT, then you might be able to find a well-paid job. On the other hand, there are also more seasonal jobs in hospitality, which might be more casual when it comes to job requirements.
While English is generally used in the corporate world, it would be advantageous to speak French or German as well.
Unfortunatley, I can't give you any more specific details on what kind of salary you can expect in Switzerland. The Swiss are notoriously secretive when it comes to disclosing salary information. I would suggest you have a look Salarium for more specific information.
Also be sure to read our Working in Switzerland page to get a good overview of the opportunities available.
Good luck with your job search.