[Paula]

I think what I would do is focus on pigs at the moment, particularly if you're also somewhat new to pigs.

They're different animals with different nutritional needs, different health concerns, etc., and I think what I'd do is learn as much as I could about one before expanding to another or you may very well end up way over your head.

Rats do require a lot more in the way of one on one interaction, as Skeetersmom pointed out, and that can't really be done by putting them in a ball and calling it good. They genuinely want to spend time with YOU as much as possible. While they don't absolutely have to be kept in pairs or groups, they are social animals, like pigs, that thrive with companions of like kind.