for a 55 year old
salary could be around 2m won to 2.2 a month, single studio, no split shifs, 5 days a week.
Watch out for schools not giving you a contract (signed)right away because your age, some of them like to wait a bit to see if you are healthy enough to fit into their long term plans (1 ear or more). As always, all will depend of the chemistry between you and your director.
Others, you should have no probelms finding other foreigners English teachers to communicate with. Korea has a bunch of them. imho korean people like extra polite foreigners, no need at all to learn to speak korean, only use these words, anyunhaseyo for hello/good morning and kansanida for Thank you. Also a friendly smile.

Good luck in Korea, Dan Park (Seoul)