Like Don, I live in the USA. In our first settlement, my XW and I used Nolo Press books, standard boilerplate documents, and I consulted a few times with an attorney. I got primary custody and pay no child support or alimony. I understand that's good for a dad. The court didn't bat an eye. They just required us to sign a waiver indicating we knew support guidelines.
It helps that I'm in business and good at negotiating. It helps also that, whatever else was broken in our marriage, my XW still trusts me to act with integrity.