It's why I started training players when they are 19 yo. It's really annoying, that you can look at auctions list for hours and can't find a single player in a position you need who is 18 yo and a fast trainer.
Now I have time the whole season to find one and train him day 1 of the next season. Then again, I waste a year where he could be playing already if I would find a proper player on the auctions list first day of the new season.

There should be something on day 1 of the new season where you can pick a talent from your youth team or something, so a 18 yo fast trainer 3-4 stars in the position you want and yes he can be expensive like 20-30 Token but I would totally buy him.