What about a bike forum?

Getting a used bike is a good idea as even with the experience your son has had to date he will still probably have a couple of oops and drop it turning around in a tight area at low speeds. There are few 250 street bikes now that were absent from the market for a long time that are good if you stay on paved roads. A rural situation that entails gravel and pavement means he would be happier and more confident on a dual purpose bike like a Kawasaki KLX250 (scaled downed KLR adventure bike). The grip type tires will be better for gravel roads than a pure street bike. It will also allow him to travel at highway speeds when he hits the pavement. Most bikes speedometers are optimistic for the speed by 5 to 10% with most being close to 8% high. When your son thinks he is doing 110 kph he is only doing about 102. A built in safety factor for parents so let him eventually figure that part out on his own. In the dual purpose style the 250's will have a top speed in the 100 to 125 kph depending on gearing.

Hopefully you can keep him off of the 600 cc sport bikes for a couple of more years so his riding skills have a chance to catch up with the bike performance.

Whats wrong with a car ? Atleast you don't fuck yourself up even if you just fall over going at 5kph.

Even the shitiest car over the coolest and most bad ass bike ever all day long.

I would never let any of my kids ride a bike IF I had any, and thats saying a lot as I hate kids !