Paint? I thought he was talking about the engine. LOL
No really, if the car is gutted meaning you don't have very much that can be re-conditioned or salvaged, then you have an expensive road ahead of you. If you have things like interior, chrome, and components that are there but just need to be touched up or refinished or rebuilt then you don't have it as bad.
Also by custom, you are implying that you are not to worried about going back with OEM parts and factory correct stuff. This is even better for you because you will have the freedom of acquiring parts from other sources such as a rear end from another car or Summit seat vice expensive originals (that is if your car is "gutted" of even the seats).
There are ways to get around the stuff that alot of people see as being necessary for their restoration. I don't refer to my project as a restoration, that would imply that I am restoring the car to it's original state, which I'm not. This allows me to get those Summit seats because they hold my butt better and their cheaper than searching eBay for decent seats and then going to Legendary to get skins, and so on. However, I am splurging on alot of components that take my total waaay up there.
If you want a cool cruiser that isn't factory detail, well then you can do alot for 15K providing your guy is decent on his $/hour. If he is running around finding you parts and doing anything but real hands on labor then you are not going to be as happy with where your 15K takes you. If you can invest the hours looking for needed parts then you aren't investing the money in him to do it for you and he could be back at the shop block sanding or something.