Pretty much depends on which of his eye's is dominant-a right eye dom. lefthander should shoot right handed, it takes some getting used to for some, but if he learns right handed, he'll likely never know the difference...but aiming with your non-dominant eye is NOT a good idea, it takes MUCH more practice than shooting with your off hand.

I'd take him to a store and have him check them out, see which feels best to him.

If he's both left eye and left handed, then a left handed gun is a good bet-or maybe look at starting him off with a leveraction, or a single shot (H&R handi rifle, encore, Ruger No.1, etc.) they aren't necessarily right or left handed, Marlin leverguns are only righthanded because they eject to the right, H&R single shots areonly so because the break lever is on the right of the hammer, and the Ruger No.1's aren't handed at all.

There are LOTS of people out there that can shoot right handed bolt guns incredibly well and quickly from their left hand. it would take some getting used to to learn how to cycle it, but they do it-the biggest reason behind it being you can't always find a lefty equivalent for some rifles.

If he does pick a right handed gun, have him make sure he can easily activate and deactivate the safety, being left handed usually makes trigger guard safeties difficult (they're backwards), and bolt position (either rear swinging levers or side mounted slide safeties) are pretty hard to use off handed. You don't want him missing game because he's fiddling around trying to take the safety off, and you don't want him AD'ing either trying to take it off and reposition or trying to put it back on.

I'm a left handed handgunner, right handed rifleman, and ambidexterous with SxS shotguns...I can "change leads" between my eyes so when I'm shooting left handed, I use my left eye and vice versa-it also comes in handy when I'm shooting a scoped rifle-I can find and watch my target with my left eye, then switch and have the target in scope the whole time with my right eye, instead of lifting my head-helps with target acquisition and following moving targets.

Not that it's incredibly pertinent to you right now, but it's something to think about, I'm a left handed handgunner, and really don't like Double action revolvers because loading is a little awkward (cylinder drops out to the left, so I have to point it down and turn my hand inside out to load with my right hand-or take the time to switch hands.) Shooting certain Semiauto pistols is also a challenge, manual safeties either require two hands to deactivate the safety or require a shooter to unwrap their thumb, take off the safety, then replace it, and vice versa to re-activate the safety-not handy if you're shooting on a timeline-like a SD situation.