Don't know what state you are talking about, but let me tell you my experience in CA. Divorced with infant children. Joint custody with me primary, kids live with me. Still, required to pay child support. She won't work, too lazy. I make money so the court in it's infinite wisdom thinks me taking care of her is better than her being on welfare. Think it sounds crazy? It is. Think I need a new lawyer? I have the best money can buy, that's why I get to live with my kids. The bottom line is, spend the rest of my time, energy and money fighting in court while both attorneys cash in or just pay her.
In Nebraska, child support is calculated according to a formula. I don't recall it exactly, but it is basically a fixed cost for the child based on a percentage of total income, then assessed against the parents in proportion to their share of the income. That only applies in joint custody, mind you, and in cases where the wife is a total deadbeat or working some worthless job, you better believe the father still gets stuck plenty hard.
But if incomes are roughly comparable, there may be little or no child support ordered from either party.