As a beginner I would go for a bic board.... not as cheap, beginnery (uncool!), heavy, bulky as a foam but not as fragile as a fibreglass, and more userfriendly but has a wide range of sizes/widths to look at.
Many decent surf shops will have secondhand boards which is what I have and as surfermummy said, have a look on ebay!
Also you need to think on where he will mostly be surfing and his size (length & weight) this will all determine what sized board is best x