It is basic figures about sales of language learning:

The numbers of each of the following answers for the market in:
USA, Japan, China, UK, Germany, Korea, Australia

Sales Value in US$ per year for language teaching on courses with teacher?
Sales Value in US$ per year for language courses on CD-ROM/Web without teacher?
Sales Value in US$ per year for language distance learning?

Persons studying language teaching on courses with teacher?
Persons studying language courses on CD-ROM/Web without teacher?
Persons studying language distance learning?


The 5 largest companies selling language courses by turnover?

Which Countries ahs the largest market of language studies?
The most studied langauges?

I don't know about sales of language learning in USA, Japan, China,
UK, Germany, or Austria but I know something about Korea.
Koreans are obsessed with English.
They would be tons of money to learn English perfectly. I personally
experienced in Korea one time when I was visiting Korea.
I was just walking on the street and this guy came to me and asked me
if i was interesting in teaching English to middle school kids. The
deal was like this.
I only had to work 8am to 12pm a day, which woukd be only 4 hours, on
Monday to Friday and they would pay me 2,500,000 Won which would be
approximately little more than 2000 US dollars.
It wasn't really hard to teach 11 or 12 years old kid and I also got
along pretty well with other Korean teachers, too.
I don't think this would help you a lot but at least it will give you
an idea how easy it is to earn money by teaching English in Korea.

I meant 2000 US dollars per a month