The most recent "Why I Write" segment on the Guardian Unlimited Books section is an interview with science fiction/mainstream writer Iain M. Banks. Interestingly enough, he's the only writer I've seen willing to say he became a writer because it was easy for him and he could make money at it. According to his Wikipedia entry, he used to own a Porsche Boxster, a Porsche 911 Turbo, Jaguar Mark II, a BMW M5 series, and a diesel Land Rover Defender, so he obviously did well with his chosen field.

And even though this interview is listed under his "literary fiction" name of Iain Banks (as opposed the to Iain M. Banks he uses for his genre works), he also said he didn't have a favorite book as a child, only a favorite genre—science fiction!