There have been many attempts to interpret Korean rental housing market, where distinctive rental contracts including Monthly Rent with Variable Deposit(MRVD) and Chonsei as the two extreme ends of general MRVD have co-existed. Although there have been some advances that interpret the function of the deposit in MRVD as a leverage, those trials were not completed. In order to develop a new partial equilibrium model of Korean rental housing market, this paper incorporates the default risk of the tenant in the model. The theoretical results show that deposit-to-monthly-rent conversion rate increases within a certain range of MRVD where the deposit can not cover the total amount of monthly rent during the contract period. Also, the empirical results confirm that there exists the premium for default risk of tenant in the form of a higher conversion rate when the amount of deposit is less than the total amount of monthly rent for two and a half years. it shows that the market conversion rate varies by the ratio of monthly rent to deposit differently from the conventional belief on an unique conversion rate indifferent from the relative deposit amount.