225 RiverStar Building in Gangnam (2) – PART 2

"The total floor space of the building in Sinsa Town is about 5,000 pyung. How much rent do they charge per pyung? Let's assume the rate of revenue as 6% of the investment amount. Since the building is located on the main road, it should be about that amount."

"Say, the investment amount is 200 billion won. 6% of it is 12 billion won. If I take a loan for 80%, I can use only 40 billion of my own cash won instead of 200 billion won. How much would I be paying for the loan interest then, assuming I borrow 160 billion won? If the interest rate is 3.5%, it's 5.6 billion won. If I subtract that amount from the potential annual revenue of 12 billion won, I will be left with 6.4 billion won."