Well there's lots of good advice here already, but here is my 2p. I'm not a commercial pilot, but would have loved to have been one when I was 18. In retrospect though, I don't think it would have been a good life choice. (I do love flying, do have 300 hours gliding, which was enormous fun, and did have to stop for medical reasons, so that would have messed up the commercial flying career anyway).
Your son should think hard about what he wants to do. If he wants to be a commercial pilot, then ask himself why? It's a very specific goal. Or does he love flying ? That's a more general goal, and possibly more realisable? Does he love the tech of flying? Again, a more general goal. And in any case, whatever you think you want to do at 18, as you mature your goals and desires often change.
As others have said, he is young and that gives him great opportunity. Being bilingual is also an advantage on his peers. Why does he need to to rush to be in the seat of an A320 in his twenties? (apart from the general argument that if you don't put everything into achieving that goal it just may not make it all, as life's distractions get in the way). I would suggest that he thinks about (a) getting an Engineering degree related to Aviation (if he loves flying that ought to be an interesting thing to do), that he does as much flying as he can afford while he does that, maybe with some parental loans (sadly the degree cost a lot too....bum), and meanwhile tries various different types of flying where he can. Do as much of the modular route as he can, according to finances. Try some gliding, do the PPL route, maybe get to be flying instructor, go and look at the aviation engineering job market, go to flying clubs and talk to the instructors there who will have a wide range of experiences (at my gliding club there were military pilots, 747 pilots, a guy who lead part of the Airbus wing design team, and a guy who was the chief pilot for the British Antarctic survey - they were all just normal guys and eminently approachable). Talking is free and you can learn a lot that way about the aviation industry (and life in general). If the flying does not work out, having a degree is a good thing to have in terms of getting a job outside flying.
Finally, it's clearly bloody hard to become a commercial pilot these days. But tell him not to give up, just because it's hard. I was fortunate and went to Cambridge in the 70s to do engineering. I have a picture on my study wall of me in a rowing eight on the Cam. Sitting just behind me is a guy called Mike Foale, another engineer, who graduated a year later after me. He got a PPL shortly after he left Cambridge. Fifteen years later he flew as part of the crew of Space Shuttle STS 45, and eventually he flew six times in space. It just goes to show you can do anything you want, if you try hard enough and you are lucky enough to have the opportunities.