>I'll report you to the BBB, file a law suit against you and pre up a class action law suit to rape you into bankruptcy and make sure no one will ever do business with you again.
No, you won't, because unless you're a lawyer even thinking about it for too long will be more expensive than the license in the first place.
This happens a LOT.
Your client doesn't pay within 90 days. Do you automatically sue them? No. Do you refuse to work with them in the future? It depends; if you automatically rejected every client who breaks the contract by not paying exactly on time you probably would run out of clients very quickly.
You need to be in the hole for something like $50,000 before it's worth the money involved in suing someone. So most of the time people cut deals and work something out.
Let's suppose you're underwater on your mortgage.
It's hell on your credit rating, but if it's not your DREAM HOUSE you'd be stupid to stick with the loan.
Let's suppose you bid on a construction project, but a machine somewhere broke and you can't afford to replace it. Finishing the bid will make you go bankrupt; it's more rational to break the contract.