There are several warning about teaching in Korea here (below) and on daveseslteachersboard.com Basically you should be asking for 2 million won a month, no Saturday teaching, no rent for your apt. as it is just a 1 year contract, and you should ask that your pension be paid in monthly installments as it is often stolen by the employer at the end of contract. Sorry but true. Ask for your hospital health card the week you arrive, and keep asking. The first time you go to a hospital clinic take a Korean with you. The tax rate is 3.4% on your earnings so don't let anybody con you and take 8 or 9 %.
Good Luck!