As a HVAC contractor in SC, I normally ask for 1/2 down on contract
jobs, and get it. Huwever, I normally provide a 3 to 4 page WRITTEN
proposal that we both sign and date. It spells out what I will do and
what I will not do, the payment terms, my insurance, extra charges for
changes and any discounts for options not taken.

Next time get it in writing and pay by check. Doesn't need to be
typed, but should have his name and address & your name and address.
Small operator like that probably can't handle credit cards.

He sounds like a real jerk. Still send him the letter, return receipt
requested so you have proof of delivery. If he refuses it, you may get
proof of that also. Then go to small claims or magistrate court.
Filing fees are added to the award in many states. If you lose, it
will only cost some time and the fees in most cases. (Check with the
magistrate on that). Worth the try. He may be doing something ilegal
if he has no license or tax certificate. Check your local government
jurisdiction. Some areas allow work without license, some do not.

Good luck.

Stretch