In the Korean real estate market, distinctive rental contracts including Pure Monthly Rent, Monthly Rent with Variable Deposit(MRVD) and Chonsei have co-existed. Conventionally the deposit in the office market is assumed to be put in the bank, and the landlord gets interest income from it in the cost of corresponding monthly rent. However, the deposit is used to reduce the equity investment, that is, as leverage and no interest income is produced from it. Because of this misconception of the role of the deposit, the conventional way of calculating earnings rate can be misleading. Therefore, an acceptable way of calculating the rate of returns is required for the distinctive Korean office market. This study examines five methodologies differentiating the role of the deposit and the base rate of deposit considering the function and the portion of deposit in MRVD. And then we apply the five methodologies to the empirical comparisons using the data of Korea Association of Real Estate Investment Trusts. The empirical results show that the interest seeking methodology is likely to underestimate the actual investment performance. Interestingly the rate of return based on the leverage treatment of the deposit is most similar to the internal rate of return. This is one evidence that the way of earnings rate calculation with the treatment of deposit reveals actual investment performance in a better way.