To work or live in Korea, you need to find out which visa will apply to your specific situation. The most common visa that expats use is an E2 Visa, which enables foreigners to work as ESL teachers. Other types of visas include but are not limited to F7, F4, E7, F2 and F2-1 and are for different situations/jobs.
In any case, you will certainly have to apply for your Korean visa while still in your home country. It is advisable to become familiar with your country’s Korean embassy that is closest to where you live and keep their contact information on hand for any questions that may arise while you research the type of visa that best suits your situation.
For each unique situation, you will require a specific Korean visa. If you think this is a confusing process you are absolutely right! Korean bureaucracy is, at best, confusing for any expat and is usually the main source of complaints you will hear from fellow foreigners. Often, dealing with Korean immigration officials is a headache, but remember: your experience in Korea will be well worth the confusion if you go with the right attitude.
The Learn4Good website will help you decide which visa will best suit you:http://www.learn4good.com/travel/south_korean_visas_requirements.htm. While this website is a great source, your local Korean embassy will always have the most up to date and accurate information for your visa needs.