I'm still a newbie to handguns (<10 years) and can easily remember all of my mistakes. I only considered hunting with a handgun 4 years ago and have been practicing and experimenting since but still haven't squeezed the trigger on a deer.
My first hunting handgun was an Encore in 7-08 with a 2-6 scope. Great gun, super fun and accurate but I didn't like the size and bulk and no way I'd walk the woods with it and it's long gone. To me it was like carrying a 6lb carbine with all the disadvantages of a handgun. Key word is walk, if he's a stand hunter it might be fine...
Second 'hunting' handgun was a SW686 4". Another great gun, I carry it a lot and shoot it regularly, but not really a deer gun and I would never try for a deer with it unless it was self defense. I tried the .44 mag 629 and unless scoped, no way I'm attempting over 50 yds with it so on to Contenders.
My third hunting handgun was a Contender .35 Rem 14". That's another keeper, amazing accuracy, fun to shoot with the muzzle brake but it's big and bulky to carry and hard to shoot off hand. Any large caliber muzzle braked handgun will seriously damage your ears even with 1 shot and it's not easy to stalk and stillhunt with hearing protection so it mostly stays home unless I'm going to sit all day.
My last hunting handgun is a Contender 10" 30 Herrett. This is the one I will carry most and think it's perfect for a newbie to hunt with. A 7TCU or similar round designed around a 10" barrel would also be great. The 10" Contender with a 1-4X or 2X scope in nice to carry, nice to shoot and although it will be bad I'm sure, I would take 1 shot at game with it unprotected. One hundred yards is easy with it (groups just over 1.5 inch with most everything, better with some), 150 yds is still OK.
Like the other posters, I would strongly recommend a .22 as his 1st acquisition, let him burn up a dozen bricks of ammo, then start thinking about a hunting gun.