Is it worth it to set up a "how to teach" web site? Look around the new and you'll find some of the best money making web sites are sites that teach other how to do something. I hope that you have heard stories of piano courses being sold online. Also web sites that teach how to play guitar are huge markets that people want to learn how to do.
I was recently watching an online video and they took me to You Tube and they showed a video of a guitar player, I don't even know where he was, but this guy had millions and millions of hits and he was an expert at playing guitar and he was using You Tube videos to promote and sell his product because on the You Tube video, right to the right, you'd have a link to the website and I'm sure once you link to that website and he's capturing an e-mail address and a name and he is selling his guitar information product.
I've got my kids both in piano. We have a piano teacher who comes to the house every week and we're trying to teach them how to play piano and it's pretty hard. We pay for the private tutor, but yes, I think it's a great hungry market.
I'd say do you research. I'd say call some of the product developers. I'd go on Amazon, see what kind of How to Play books are selling there on Amazon. I believe they'll tell you the positioning, how popular it is. Do your research and you'll find your answer.