My main tip would be to stick with a shelter, rescue, or classified site like Craigslist. Other than that, be very, very sure of the sex of the companion piggy. The shelter I got Borat from said he was a girl, so I commited to taking Amy from someone on Craigslist and then found out he was a boy...oops! Neutering will fix that soon, but it's easier to be sure of the sex in the first place. I'm sure Butters will be happy to have a friend.