How do people afford to have kids?

Most people that have too many kids will depend on the tax payers to feed them and give healthcare such as Medicaid until the age of 18 or longer, if they are born disabled.

sign up for welfare

maybe that's a sign you shouldn't have them. or you should adopt or foster. you get paid to foster.

You give up certain things in order to afford what you really want.

Example - before children - my husband and I would go out to eat two and three times every weekend and go to at least two movies at the theatre almost every week.  We also spent money on things we didn't really "need" but just "wanted".  Those things are unneeded expenses and that changed after we had our children.  We ate out less and went to fewer movies.  That money saved was enough to cover the diapers and many of the basic needs for the baby.  Having good insurance is a great bonus so that you don't need to worry if your baby does have medical needs.  

Think about anything you spend that you don't actually need - how much money is that and then go price diapers and other basic baby needs.  You will be surprised how far that extra money can go.  

We raised 7 kids and own a ranch, so needless to say we aren't rich. You learn how to stretch a budget. If you want something, like my wife wanted a big family, there's always a way to make it work.