I love border collies!!! I had a border collie growing up (he just died a few months ago at the age of 12 or 13
). They are awesome dogs! I really want one again someday. We did not have a cat but we had a bunny...and yes he did herd the bunny. The bunny never got hurt but the poor guy would get chased around and cornered if we weren't watching. Also, be careful if you have young kids. Our border collie would also herd us and nip at our heals when we were running around and playing, but we were old enough that we were ok with it (I was 9 or 10 when we got him). I imagine you can try to train them not to do it but it is still instinct and it can happen!
Also, they are working dogs and do need/like exercise. So a decent sized yard is needed for them. As for a job, anything will do...obedience, agility, tricks, even retrieving the ball will work, as long as they have something to do
We just taught him a lot of tricks (they are SOO darn smart!) and practiced those with him daily...and he was constantly bringing us toys for him to retrieve...that was his favorite job.