I agree that two are definitely no more trouble than one, but they are twice the enjoyment. I vote for a friend for Josie!

I think any age would be fine, but if you went with older it should be an easy going cat that is used to getting along with other cats. I know kittens usually are welcomed in pretty easily, but there's no strict guidelines. If/when you start looking, whichever kitty picks you is the one to get.