Make it easy and simple in the start, let him have a class 1 medical, do a PPL - and if still motivated start the ATPL's.
This will not set you back the world, but if he finishes the above, you can start to worry, then you know if he is really motivated. Do modular, forget integrated at the moment, unless you don't mind blowing an extra £40.000.
He is young, and time for a few up and down cycles, and should get the "dream job" in the end.
Do modular, make him get instructor rating, and work himself slowly up the ladder, by his mid 30's he should be well established.
But first do the basics, might be dead in the water already then, class 1 + medical, and do the 14 ATPL ground school exams, won't cost you more than £8000 - £10000.