Housing market stalls, Price of housing drops, Home owners with large mortgages walk away from their homes and buy new ones. (no point in paying a $400,000 mortage on a house worth $250,000). The bank is then left with a property instead of actual money. Houses are sold for less, Banks lose a significant amount of money, Bank increases interest rates to regain some lost funds. People pull money out of stocks and pay off bank debt to escape rising interest rates, and in the end the stock market goes in the shitter.