Bought from own savings and income 4 years ago with no help from parents, not a family-owned apartment or sizeable inheritance. Owner is an immigrant from a developing country, the exchange rate alone would be prohibitive for any family assistance.
IIRC the housing market in the Netherlands 4 years ago was way more accessible than the madness of today so that's probably not a surprise that he could afford it. Ask him if he could have bought in the market of today please.