Or if you do work as a freelance contractor, you can pay a business lawyer 4 to 6 hours of their time to draft up a services agreement that you will use as a template for every client going forward.
Client doesn't pay me (after some nudges that they should)? Well according to the services agreement there was no IP transfer, because I wasn't paid. They continue to use the IP? Well the contract they signed says I can sue the hell out of them (and win) as recourse. Client wants something changed after delivery and payment? I'm not obligated to do squat, as the service agreement says that since they signed off on the delivery receipt, they supposedly were fine with it. The services agreement makes sure I get paid, the client doesn't try to put me over a barrel, and makes sure I'm making good by my client. That's what you have them.
Seriously. Always have a contract.