Overseas students from countries that are not part of the EU or EEA must not work for more than three months a year (90 days full time or 180 days part time) without a work permit. It is very difficult for students to obtain a work permit
Exceptions are made for students who work as research assistants at the university. In this case students are allowed to work for more than three months a year during the studies. The work department checks up on this and it must be authorised by the foreigners department. Student research assistants are paid about 8 € an hour. Students must not work for more than 83 hours per month.
Students from EU or EEA countries (Iceland, Liechtenstein, Norway) and Switzerland do not need a work permit and there is no limitation to the amount of hours they work. If working as a student research assistant they must not work for more than 83 hours a month either.