My personal limit is 2, as I adopt older cats and have a knack of finding cats that have health issues and cost a fortune (vets bills hte past 2 years have been in 4 figures each year, and the bulk is just on one of the two cats), and i dont want to be in a position where I have a third and can't afford the food or vet treatment. I do foster though, so get my kitty fix that way. Everyone has their own limit and it really does depend on things like space, finances and time. But dont knock rescues for asking why, we generally do it to make sure people have thought things through and are doing it for the right reasons, sometimes people do it for themselves with no thought of how their existing cats will cope, and if it doesn't work out, the cat has been messed about for nothing. Also, it might make a difference as to what cats they think would be suitable - we got asked about one of our 10mo's today, as another rescue had said that age group as a friend, yet ours are mega hyper and it would be brought back due to the existing cat not appreciating it. IF we hadn't known why, we might have said yes and got her hopes up unnecessarily.