When it comes to housing in Korea the following terms may be useful:

• jeon-sae ('chun-say', 'cheonsae', ...), also called 'key money', is a system where the renter pays a flat fee, around 60-70% of the overall value of the property, when they move in or sign the rental agreement. The landlord invests this money (puts it in a bank account, etc.) and keeps all of the interest earned, then returns it to the tenant at the end of the contract.
   
  During the length of the rental contract, usually one year, the tenant pays no additional rent - the initial jeon-sae/'key money', is the only payment made to the landlord. Other bills (electricity, gas, phone, security guards, cleaning ladies, etc.) are, of course, still paid by the tenant.
   
• wal-sae ('wuelsea', 'wall-say', 'weol-sae', ...) has two types. The most common involves a large deposit (also, and somewhat confusingly, occasionally referred to as 'key money') ranging from 5-10 million Won (approximately $5000-$10,000 U.S.) up to 100 million Won or more (over $100,000 U.S.). On top of this, the tenant pays a monthly rent. As a general rule, the higher the deposit, the lower the monthly rent.
   
  When you see a housing ad listed as 500/50, for example, it means the landlord expects 5 million Won as a deposit, and 500,000W a month as rent. A bit higher up the scale, 3000/80 would mean 30 million down, and 800,000W a month. These agreements are normally for one year.
   
  There is another type of wal-sae, though this one is generally limited to upper-income foreigners (sent here by their company, government, etc.) in a few areas of Seoul. This type involves NO deposit, only the monthly rent. The rent is paid in one lump sum at the signing of the rental agreement. Rental agreements of this type are usually for two years.
   
• 'villa' - no, not a luxury place on the Riviera! In Korea, a 'villa' is a small apartment building/complex, generally consisting of buildings less than 5-stories high. They may or may not have security guards and maintenance personnel.
   
• apartment - these are larger buildings, usually gathered into giant complexes of identical structures, found throughout the country. They are over 5-stories high, and nearly always have elevators, covered parking, security guards, and maintenance personnel.
   
• 'house' - relatively rare in Korea's larger cities, with high costs generally limiting them to expats stationed here by their company or government.
   
• 'officetel' - the word, and the building, is a combination of 'office' and 'hotel'. These are usually large buildings with combination commercial and residential areas. The residences usually come as furnished studios or small one-bedrooms. Officetels are most commonly located in the popular business districts of Korea's largest cities. Since officetels are usually newer and far better furnished than similarly-sized apartments and villas, they tend to carry a 10-20% price premium.
   
• 'pyong' - the traditional Korean measurement of housing size. One pyong equals approximately 3.3 square meters. Though now undergoing a government-mandated shift to square meters, it's still quite common for housing to be quoted only in terms of pyong.