According to Keki Mistry, vice chairman of Housing Development Finance Corp An increase in the housing supply, rising borrowing costs and a stock market rout are bringing a five-year property boom in India to a close, according to executives at two mortgage lenders. Property prices across the country could drop as much as 15% in the coming months. Gagan Banga, chief executive of Indiabulls Financial Services Ltd., predicted prices could decline as much as 20%.