If they are smart and refuse to pay you, then you accuse them of a lie designed to hurt them, and email them an invoice that includes a threat that if they do not pay, you will spread lies about them on Google.
This is now widespread across America.
2. You meet a group of freelancers for lunch. You don't hire any of them. They send you 1-3 emails during the following week asking questions about your project. Three days later, they invoice you. They have not actually DONE anything. You are being billed for the emails they sent you because they're about YOUR project, after all.
3. You ask a person a question on the phone. They answer you. It takes about 30 seconds. Three days to a week later, they invoice you $2500.