well, you are breaking the rules…it’s not up to be to classify sin - only you can really do that.
As a side note, it’s REALLY not wise. Your cat may be well behaved, but it may have bladder problems later in life, or get panicked one night and tear up a wall or blinds. Not to mention apartments typically have open ventillation and someone could be living in a “no pet” apartment complex due to severe allergies - in which case you could send them to the hospital.
Then of course, there is the fact that if you get caught you face eviction or being forced to give up the cat.
Is it too late to find an apartment that allows pets? We have several pets ourselves, and I couldn’t dream of giving any of them up, but it’s worth the extra work of finding a pet-friendly place than run the risk of losing our cat, or home or sending some with severe allergies to the hospital.