A method according to claim 8 wherein the customer purchases all or part of the interest, and the percentage interest in the property being acquired by the customer is calculated as follows:

PIBP = FP/PP*a/b*100 where:

PIBP is the percentage interest being purchased;

FP is the funds provided by the customer for the purchase;

PP is the total purchase price that was paid by the customer;

a is the property price index for the last day in the calendar quarter which has most recently passed for the area where the property is located; and

b is the property price index for the last day in the calendar quarter which was immediately before the day of purchase