Whoa whoa whoa! U21? NT? Now I'll agree that targeting the U21 guidelines isn't a bad idea given that that will create a very solid player, but nobody should start out BB and training their very first guys with either the NT or U21 in mind.
Now, if the original poster decides to try and sell him, that's cool and all, though 1 million might be a bit high on a guy with 7 potential, especially as he's about to age a year. I definitely suggest joining up at the offsite and at least asking other folks what they might pay for him. THen the option of selling will be clearer whether it is a good idea in the long run.
As far as training versus buying veterans, that's a purely personal decision about how each person likes to play the game. If you like to try and promote into D3, then selling this guy, expanding your arena, and buying trained veterans is one way to go. If you want to train young guys for your team, develop them, and slightly delay promoting to D3, that's another way. Both have their pluses and minuses, and I don't consider one as "better" or more valid than the other.
Still though, at least a level 4 trainer is the way to go if you're gonna train him up. And also you might as well get another young guy you can train along with Bruno. Maybe you'll be able to get someone in the draft.