A way to (partly) finance your studies in the Netherlands is to get a student job. It will be an advantage if you are able to speak the Dutch language when finding a part-time job.
(also for Switzerland, not from Croatia)
As a citizen of a European Union member state you are allowed to work unlimitedly in the Netherlands. You need to make sure, however, that your work does not conflict with your studies and impedes your performance.
Non-EU students who wish to get a student job need a work permit (TWV). Your employer needs to apply for this permit on your behalf. Non-EU students can choose between working for a maximum of 16 hours per week or a full-time summer job during June, July and August. It’s not allowed to do both.
You do not need a work permit for your internship or thesis period if you have a valid residence permit. However, HAS and your employer need to sign an internship agreement. Please note that exchange students (non-EU) who will come to the Netherlands for an internship only, still need a work permit (TWK). All you need to know about working in The Netherlands can be found on the Study in Holland website.
Please note that once you take on a student job you need to get the Dutch basic healthcare insurance. More information about health care insurance can be found on the website of Study in Holland.