No Pets building?

Do any of you guys have experience with living in owner-occupied apartment buildings with a no pet policy that actually strictly enforces it?
Specifically, the co-op I am thinking about buying into states absolutely no pets, but do you think they would really care if I have one very elderly quiet cat?

My current rental also has a no pets policy stated on our lease but many people have cats and there are even a few people with small dogs and to my knowledge no one cares. It seems like the policy exists just to back up the landlord in case any tenants cause animal-related disturbances.
Nonetheless, I am hesistant to break a rule in a co-op because it seems like there are more people trying to enforce rules in co-ops.
Help, I need advice!