Put 10 kids in a 'classroom' and charge each ones parents $15 bucks for the hour. I'm located in the mainland, the people who learn english privately can afford to shell out the big bucks. English is expensive. What would you pay for an expensive starbucks coffee or a pizza... a gourmet pizza in the main land? Its 100 rmb here for a pizza. Foreign/Imported goods and services are expensive.
This is only really possible with kids because everyone and their mother HATES teaching kids. I suppose in the comfort of your own house it might be a better deal...but 8 kids... yuck. A typical class consists of you playing boring games with flashcards and then yelling the word on the flashcard at the top of your lungs. If you can stomach this kind of sh1t on your days off then you will probably make bank. The kids teachers are typically the highest paid and the most in demand. 300 rmb seems to be the going rate for teaching adults per hour... thats about 45 bucks. Usually the schools pay enough so that you dont have to do extra work on the side...theres nowhere here to spend it anyway... once you've got a woman, apartment, computer and video game system... what else do you spend your money on? Anything that I don't spend on food or rent now just goes right into the bank.
Another 'hustle' would be to recruit teachers for interviews. I get 15 bucks for every teacher I find and recommend to the school. Usually I just approach every white guy I see walking through the railway station.
Private lessons are the main side job for most teachers. If you are REALLY good at getting lessons and schmoozing with CEOs then you can recruit a bunch of people and pay them on their days off to work a couple classes for you. I use to teach in Brazil for a guy who ran a 'school' out of his house. He hired me out to his private students and would pay me about 35 bucks a class, I thought I had died and gone to heaven. Later, I found out that he was charging 100 bucks per class for the students... I was still happy though, got tons of work from him. He absolutely loved money, also drugs...which is what eventually sank his business. If it weren't for that, he'd probably be making crazy $$$ right now.
Private lessons are a great way to make extra cash because you are selling your time... and if you teach adults, usually a lesson consists of talking to someone about what they did last night, thier bf/gf or a movie/videogame they played recently. In my current job, I talk about sports/games/whatever for a 45 minute session and make about 25 bucks. I also do kids classes....ugh. Having game really helps here because you can basically just run game on a woman for 45 minutes and get paid for it. At least all of this studying hasn't gone to waste right.
http://www.daveseslcafe.com (if you want to teach kids)