You can start self-funded, but then it will not be an easy road to take. Find out channels to financially support your research!
Check the guide for funding, ranging from fundamental research, applied research, specific topics on Brussels to international mobility: https://intranet.vub.ac.be/research/guide
The doctoral schools gives financial support for calls for activities that are mainly targeted towards PhD researchers, for going to conferences, summer schools and short stays abroad via travel grants, and for language support, for example before you submit a paper to a journal.
Depending on your funding, you can get reimbursed for activities/expenses related to your PhD. Check with your faculty or department secretariat: https://student.vub.be/en/phd/contact#who-to-contact