When I used to live in CO I had to drive by a hog farm every day to get to work. I can't tell you how glad I was when that job ended. Ugh...
I'm fairly confident that a potbelly pig (very different pig from the ones raised for food) are actually quite clean indoor animals. The bigger issue, from what I've read, is that they are smarter than dogs, and require more attention and entertainment, less they get bored and get into things, knock things over, etc. For example, I hear they can usually learn to open the fridge, so one would probably want to put a lock on that. You'd basically want to take the same measures a parent would to toddler-proof their house.