What are the visa & residency requirements in Seoul?

"In order to visit Seoul, visitors must obtain a visa prior to their arrival. The process of applying for a visa involves submitting an application form, a valid passport, a passport-sized photograph, and the applicable visa fee. Depending on the purpose of the visit, additional documents may be required. In order to obtain residency in Seoul, Korea, applicants must submit an application form, a valid passport, a passport-sized photograph, and the applicable residency fee. Depending on the purpose of the residency, additional documents may be required. Additionally, applicants may be required to provide proof of employment, proof of financial stability, and proof of health insurance. Once the application is approved, the applicant will receive a residence card, which must be renewed every two years," mentioned another expat when asked about moving to Seoul, Korea.