Good plane, but expensive. Both to purchase, and operate, for what you get.
If he is doing training now in a 182, then a 206 would be a fairly easy move. If he is in a 172, go take him out in a 182 for 5 hours or so, to get him really familiar with how it lands/handles different than the 72. Then let him know the change to the 206 will be about that much more. I'd strongly recommend getting into a 182 as soon as possible if not already though, so he gets used to everything happening at a faster pace. Not overflying patterns, learning how to slow down and decend a high performance plane. Throw some friends of his in the back, and do landings when he first gets it in addition to just doing it with the 2 of you up front. Move people around to show how CG changes effect performance. Discuss extensively issues of a too forward CG if he wants to go fly it solo sometime
Good for you, you get to teach him a lot about knowing how to do W&B, and HP procedures. And, fly with him a lot in it, since he'll likely need a lot of time for insurance reasons.