The bottom line is that if you play what you want to play, "rock" or "folk", you are going to do it strictly for love. If you play what a large audience wants to hear, you can make money.

There certainly are more opportunities to play rock/pop music for money than to play folk music. Given that, I've seen plenty of evidence that it is possible to make a living playing folk music, and I think that, in terms of making money, the kind of music you play isn't as important a how you present it.