First off, I need to make it clear that when I (and probably most TASers) talk about pet pigs, we mean 'pet' in the same sense as pet ponies, sheep or chickens
They live outside, in as near a natural environment as possible and certainly with other same species for company. The only kind of pig that's suitable as a house pet are guinea pigs!
Kunekunes with their smaller size, growth rate and appetite (and super friendly natures) are ideal permanent/pet pigs. As adults they are less inclined to root up grass and can be used to maintain ground in the same way sheep or any grazing animal would. But, they still need housing, fencing, regular medications and males should all be castrated unless you've got a stunning example of a boar and a buyer looking for a breeding boar - castrations for Kunekunes are best done by a vet and the cost can vary from £10 to £60 per piglet..... The BKKPS website has a lot of information on it and a discussion forum where you can ask questions.
I would strongly discourage you from jumping straight in and starting breeding though, it takes time to learn the do's and don'ts and get a handle on pig husbandry.......you might find you like the idea more than the reality. Also, supposing you bred a litter of piglets and found you didn't have any buyers, do you have the space, time and funds to keep them or raise them for pork? Sorry, don't mean to sound negative, but the amount of people I've met who think you just put them in a field and leave them to it is unbelievable and they wonder why their pigs aren't happy, healthy or flying out the door to eager buyers.....
People who keep pigs and breed them do so (usually) because they love pigs or have an outlet for pork........if we wanted to make money we'd have 9-5 paid office jobs