Number of kids and why

Ideally, about 3 kids would be nice. I have one now and I'm an only child. While I wasn't lonely and loved having the attention to myself, I think I would want to give my daughter a sibling. One reason is because I really like newborns and infants, so I wouldn't be satisfied with just having one. However, people with multiple children do tell me that there is a vast difference between having one or two children, but not so much between 2 or more children. They look really exhausted because they have to run after their children and send them to classes. There's also the issue of finances.