Is teen prostitution common in Texas?

I was watching a story on Yahoo! about a thirteen year old girl who was arrested for being a Madam at a nightclub in Texas. It later went on to say that teen prostitution is common in Texas. I didn't even really know about teen prostitution until now. Sure I have heard little bits and peices here and there, but not much. Is it common anywhere? How do teens prostitute so often if they are underage?