PROBLEM TO BE SOLVED : real estate of rental business owner to job procuration paid out from a minimum amount of rent, rent independent of the amount of real estate rental business procuration. SOLUTION : estate lease management procuration management server 4 includes a processing section 45, the base 46 of rental apartment building information regarding the management information is registered and, in the construction shown the amount corresponding to a predetermined ratio of price, 1 to be paid annually estate owner is calculated as a minimum guaranteed rent, management information of the base 46. Selected drawing : fig. 2