Then the court has many other ways to do it, just how much does

For example, if he has businesses, then you can use business valuation, or the court will look at his expenses, how he paid for all these. If you don't have money, maybe the court can make your ex pay for the attorney fees, if the court finds he is lying or hiding, then court will fine him badly. My ex buys and sells stuff, cash based, but my attorny subpeonaed the businesses he does business with, and found good evidence that he was doing business and working even he was denying it. If necessary can also subpeana all his bank accounts even other relevent people's bank accounts to provide tansaction records. My attorney also works for other clients to find the other party's assent in foreign countries. There are many ways to do it, just find out how much it costs you, vs. how much you can get. If you know that your child's father has significant assets or cash income, it is worth chasing him down. Not for you, for your child's goodness. Your call, of course.