Why does he want it? If for code questions, then he needs the one for your area, along with any local amendments the building department has added. Therefore, the local building department is usually a good source for it.
If he's a homeowner, I'd start with the Codecheck series. It's written in layman terms. However, I wouldn't do ANYTHING before showing your design and plans to your inspector.
If yr not planning to get the deal inspected, then you should read and learn the UPC. Plumbeat Emptor.