http://www.canuckabroad.com/overseasjobs/korea/schoo...

Teaching English Part-Time

Many full-time English instructors teach part-time as well, either at another institute or in privately arranged classes. In principle, private instruction is illegal; however, many English teachers do have private students. Part-time instruction at a second institute is possible with permission from the sponsoring institute and the Korean immigration authorities. Private students often pay more per hour but some instructors have found that it is difficult to sustain a long-term private class.

http://www.eslcafe.com/forums/korea/viewtopic.php?t=...

well the last time I went into why I am against teaching privates there were lots of attacks against me as a person and not what I wrote...

https://www.cato.org/dailys/06-15-00.html

It's not only foreigners teaching English who have come under attack. For 20 years South Korea's government has been waging war on any education that occurs outside the public school system. The government has investigated and fined parents and teachers--and even jailed a few. And in 1998, the president of prestigious Seoul National University resigned his post after it was revealed that his wife had arranged private tutoring in a wide range of subjects for their daughter's university entrance exam.