Recently, the housing market in Korea has experienced substantial changes in preferred tenure type. Until a few years ago, 'Jeonsei' has been a dominant tenure type. However, for the recent years, monthly rent with security deposit has taken a substantial portion of rental contracts. Low interest rate and financial reform after the Korean economic crisis have contributed to such trend. In spite of such substantial changes, there have been little fruitful efforts to analyze monthly rent with security deposit. On the other hand, the conversion rate for Jeonsei-to-monthly rent has played a transitory role to analyze the market. However, there is no consensus about the meaning and role of the rate. Furthermore, the conversion rate has been maintained at a higher level than the market interest rate. This study adopts a partial equilibrium model to analyze the structure of monthly rent with security deposit. The results indicate that Jeonsei to monthly rent conversion rate can be understood as the required rate of return of equity invested in housing rather than the market interest rate. Also a variety of monthly rent and security deposit configurations can exist even in the market equilibrium.