The following is a general comment, not about any one specific school. English language chain schools (NOVA in Japan being an exception) are often more stable than small private ones. They are more likely to pay correctly and on time.
Schools that specialize in teaching returnees deal with students who have lived in Native English countries and have a better knowledge of English than students in regular Hakwons (Hakwons = English Academy).
Many schools in Korea wanting qualified reliable foreigners on staff will offer good wages, terms and conditions not offered in other countries and above average accommodation.
By the same token, very high salaries are, at times, associated with so much work, that teachers have no time to adequately prepare lessons and very little time for their personal life.
If after researching via www.google.com and www.yahoo.com, you want more information about the school, ask them for the email address of their foreign teachers. If they dont want you communicating with the other native English speakers at the school, know that something is wrong and keep looking. If they give you email addresses, then contact the outgoing teachers privately and get the information you need to make an informed decision.
Not knowing the terms and conditions you are being offered, it's hard to advise you any further.
Hope this is helpful. Good Luck.