Around here some hotrodder's on a budget have done basic prep and priming then go to one of the cheaper auto painting places like Maco or earl shibe, and bring there own paint to them, and have them spray and color sand. I know a guy who went this route with his 55 chevy in a two tone green pattern, and got it all done for about 5500. It came out real nice. I haven't painted my own truck yet, but am going to give summits paint a shot. Hot rod magazine did a feature on it and had good things to say for the quality and price(400.00 for all of the paint to do my 48 F1 truck.) But if you go for some of the better high end paints you could be paying thousands just for the cans of paint, and then your gonna want to spend thousands to get it painted on the vehicle, so like 36 sedan said, you can pay as much as a car costs to build just for paint!
Don did a nice t-bucket for a reasonable amount of cash and didn't spend too much on paint, his build thread is project 3k here it's a great read
Project $ 3 K Is Underway