There’s a lot of problems associated with keeping cardinals as pets. First of all, there’s the plumage. Those scarlet gowns, the lace, the red caps and hats - doesn’t come cheap, you know. And the feeding! Have you seen some of them in pictures? Been hitting the local pasta shops pretty heavily, I’d say. And then there’s the migration patterns for the rituals associated with a new pope - you’d have to let your pet go on the drop of a triple tiera, with no assurance he’d be coming back - next thing you might hear, your former “pet” is now speculated as the “papabile” of the moment, or may even be seen perching on the balcony of St. Peter’s, waving to the crowds - that one’s never coming back.
Bishops are a much easier choice, or, if you’re concerned about the costs, try for a nice Franciscan or Dominican.