NY - Could I be liable for a housing discrimination charge?

I own a two-family house in New York State, and currently have an apartment for rent. Among the responses I received was an email response to my Craigslist posting from a woman who is deaf, and who also has a deaf roomate. Like all other inquiries I had, I told this woman to contact my rental agent to see the apartment. My ad stated CATS ALLOWED, NO DOGS. This woman states she and her roomate have a dog which serves as their "ears". I told her I would take that into consideration and make an exception, and explained why I had a no dog policy in the first place (too much destruction in the past). These prospective tenants saw the apartment and wished to rent it. They have adequate and stable income. They advised me to contact a woman who was the mother of one of them to learn more about them. In my conversation with this woman, I was told they also have "four cats". My immediate concern was this was going to be too many animals in one apartment, and there could be problems with flea infestation. It is true in my ad that I do not mention how many cats I would allow -- who would think to do so? I've never seen such a qualification in any apartment ad. Maybe I'm lucky, but my past tenants have had a single cat, if any at all. So, I am willing to make an exception with the dog, though with some hesitation. Could I be charged with discrimination if I don't accept these tenants for the reasons I mentioned?

You MUST make an exception for the dog. This is a trained service dog for the handicapped. This dog alerts them to knocks at the door, to fire alarms, etc. This dog should have gone through special training and you must accept it without deposit. It is covered under the discrimination laws under the ADA.

The cats are different. Your ad stated you would accept cats, but not how many. It is not unreasonable to expect that there would be a limit on the number of animals one would allow in the unit. Five would be too many for an apartment of almost any size.

Let the young woman know that you have screened their application and they are acceptable as tenants, but that you cannot allow 4 cats in the unit. They may have one and must find other homes for the rest. They will probably decide not to accept the unit, as most pet owners don't want to lose their pets. If they do decide to part with all but one cat and the dog, rent them the unit.