Kune Kune pigs are excellant for pets. They are very clever and can be trained, very much like dogs. Mine sit and beg for apples, even the boar does it!! My sow is due piglets at any moment but she will still perform for a golden delicious.
Tamworths are great for meat, but are a wee bit boisterous. I have mine behind a mains driven electric fence. I found they would check the battery fences and when the power was low, they would risk a wee shock to escape! They are excellant at clearing ground too, added advantage!!
I think its great that you're son wants to have a pet pig, but once the hormones kick in, Will he abandon it? My son wanted a dog, he saved up £350 plus for her and her jags etc, but a year later she became my dog once he'd found a girlfriend!!
Send him up to me for a day, I'll show him the "warts and all" pigs
Good luck
Lee