Working as a freelancer
In the Netherlands, freelancers, entrepreneurs and one-man statups are recognized as ZZP'ers (zelfstandig zonder personeel) or self-employed without employees. To become a freelancer, you need, apart from your registration/residence documentation, also a registration at the Chamber of Commerce. They can advise you on your individual situation. See website: Chamber of Commerce Zeeland
Registration is compulsory for every business. it is wise to get in-depth advise from an accountancy expert.
The Expat Center can introduce you to affiliated partners.