We got two kittens a year and a half ago, when DD was 5 - it's worked out fine, but I must admit I was shocked at how 'badly' she treated them. Nothing too awful (she threw a cushion at one of them, and slammed a door shut when one of them was 'chasing' her, injuring his poor little paw) but it was a surprise given that she was (is) a reasonably sensible and sensitive child, as was 5 after all, not 2. The saving grace was that the boys had been born into a household with two young boys, so were used to noise and unwelcome attention.
My head says if we ever get another cat or cats we should go for rescue, as the kitten stage is so short, but ... they were INSANELY cute as kittens, and having two was fabulous at that stage as they played together all the time. They're no longer as close as they were, but one in particular will go through the house shouting for his brother if they've not seen each other in a while, and they 'kiss' when they meet up.
Cost-wise, I've just paid £50 for two bags of food which should last about 50 days (a single big bag would be cheaper, but we can't store it). They eat dry food only - came to us on Whiskas, but quickly discovered that one won't touch wet food and the other only sucks the gravy off, so dry food it is (yay, wet food is rank). We have two carriers for joint trips to the vet, if and when they happen, a covered litter tray, two normal beds and a radiator bed that they never use, and a variety of toys! We had to spend a fair bit on getting one boy healthy when they first arrived, the insurance paid for most of the other one's dental op six months ago, and we've had to pay for antibiotics when he got bitten a couple of weeks ago. We paid for their neutering - at our vets at least, boy cats are the cheapest common animal to get neutered, cheaper than girl cats, dogs or bunnies of either sex! They've been in a cattery a couple of times, at £11 a day, but we'll get a cat sitter in future as they really don't like the (lovely) cattery.
FWIW, my friend had a kitten from a litter next door, and her boy ended up going back home to live with his mum! He used to just come and go, and now that she's moved house she's left him with the original family - she does have three kids though, and I think next door was a much calmer environment for the cat.
Also 
at black and whites being hard to home (I knew about black cats, and don't get that either) - our boys are extremely handsome in their tuxedoes.
PS tribpot I always like to hear about your cat, our cats' mother was called Harry Potter too!