What about his son (you) to give him a hand? He could really start with a blog and write on a niche (most probably on the niche related to his job). You can help him with ad placement and some marketing, he can continue writing and so on. Once he receives a decent amount of readers, i would definitively expand the earning methods to affiliate sales (if its a hot niche) which would definitively perform even better (but usually works best on high traffic sites). Hope just you two don't live in the same house and don't share the same IP, it could become nasty to have two Google accounts (even tho with different names) from the same IP (would let Google know before you even signup).