Fenners
Supercharged
Yep, slowly upgraded my way through the different engine sizes, part of the UK license system and what I could afford. Started on a 125, 175, 250, 650, 1000 now 2300.
I would have said that between a 350cc and 600cc is a great starting point - they are light with enough grunt to get you out of a situation if required. Not sure what type of bike he may like so will not offer advice there.
As @warp9.9 said it does make sense to think about his riding buddies, although that never influenced any of my choices.
Getting out and riding, to build up road sense, is the best way to keep your son safe - you can have fun on any bike what ever size it is.
Good luck with your choices and lets hope he rides many safe miles.
I would have said that between a 350cc and 600cc is a great starting point - they are light with enough grunt to get you out of a situation if required. Not sure what type of bike he may like so will not offer advice there.
As @warp9.9 said it does make sense to think about his riding buddies, although that never influenced any of my choices.
Getting out and riding, to build up road sense, is the best way to keep your son safe - you can have fun on any bike what ever size it is.
Good luck with your choices and lets hope he rides many safe miles.