I don't know what the customs are in the Netherlands but if it were me, I would at least want to see the boat rigged, sails up, rudders in place, ready to sail, just so you know all the parts are there and fit together!

If it's your first boat, you probably don't have enough experience to know what should be included and I would be very careful. If the guy is honest, he should at least offer you a test sail or to replace anything that is missing. Be careful, and try to get someone who knows that type of boat and what it should have to go look it over on the trailer before you put out any money. OR...find a local racer looking to move up, buy his boat, at least you know the parts are all there.