puppy?

Our neighbor's 10 year old son knocked on our door the other day... he asked, "Our dog is having puppies in a few weeks, you want one?" We told him we will think about it. What do you think? I really really want a dog. This one is free, and i know the dog is going to be pretty. (for your info, this is a unplanned pregnancy. The dog got pregnant by a unknown dog, not really unknown, we have a few suspects.. the brown dog, or the white dog.) They don't know the owner. I think it's the white dog. If it is the white dog, their puppies are going to be pretty.
But, having my two boys in potty and a puppy... I don't know if I can handle that. The cost of having a dog is not cheaper either.... if you have a dog, how much do they cost to keep it for food, shots...etc every year... let me know... I do want a dog, I asked "A" if he wants a baby puppy... he was very excited about it, not that he knows the baby puppy will grow big yet...