What style bike does he want?
When I was that age all I wanted was a supersport (not a good first bike), and I still love them (ride a 2014 Yamaha R1).
The kawasaki ninja 250/300, honda cbr300 and new Yamaha R3 all have the supersport look but are beginner friendly. The SV650S has a half fairing, and you can get a full fairing for the looks.
The SV650 is also good (I'm actually in the market for one to make into a track only bike), along with the Kawasaki Ninja 650.
If he wants a cruiser the 600cc-900cc bikes are plentiful and cheap (under $3k) on craigslist. Vulcans, Vstars, etc. The 250cc cruisers are pretty under powered.
Also take into account the roads he'll be riding. I almost bought a DRZ400 a few years back, but a friend that had one talked me out of it because where I live most of the time I need to get on the freeway, and traffic is consistently doing 80mph+, and the guy that had the DRZ HATED taking it on the freeway. But if you're going to be running around through the city or windy back roads that bike would be a blast.