My master thesis supervisor wants me to continue as his PhD student, but he has no funds at the moment. Any advice?
There are -mainly- two options in the Netherlands to arrange your own funding.
Get a talent scholarship from NWO. See here: https://www.nwo.nl/en/research-and-results/programmes/magw/research-talent/index.html
Or, as you are in beta science a very good option, is to find a company that will hire you and will allow you to do the phd externally. This allows you to gain some work experience while doing the phd. You will take longer, but you will stay connected to practice.
By the way, in my opinion, to much of this 'yeah i would love to but i dont have funding' is coming from professors. If they really want you, they should only offer you a funded position. But that's from someone who left academia :)