You take them to court. Try to go to small claims. I've got a suit against someone for non-payment I filed 10 years ago - it's still on the court backlog - bu

You take them to court. Try to go to small claims. I've got a suit against someone for non-payment I filed 10 years ago - it's still on the court backlog - but it was too large for small claims. And then you learn to spot warning signs, and avoid clients/projects like that again in the future. Getting some deposit up front is often a good thing, but also not something you can always manage. I've done work for govt agencies - that's generally not going to happen, but once I have a contract or PO, I've got a pretty high confidence the money will come through - it just may take weeks or months to get paid.