As soon as you can prove you live in the Netherlands (or Europe in general), you qualify for Interrail. However, if you have a non-European passport, nobody will question your residence if you travel with a Eurail pass, which does not have a limitation on travel in the country of residence.

You didn't say where you lived previously, but do note that Interrail has nothing to do with the EU and if you previously lived in the UK, you would still need an Interrail pass (with UK as country of residence).