The affordable housing fund would direct 3.5 percent of post-tax profits to projects designed to benefit Katrina victims, for two years. For three years afterwards, 5 percent of the companies' post-tax profits would go into the fund. Fannie Mae and Freddie Mac are the two largest buyers of home loans and own or guarantee almost half the $7.6 trillion U.S. mortgage market. The government-chartered companies make their money on the difference between the mortgage returns they buy from lenders and their financing costs. Fannie has said accounting errors from 2002 through 2004 could require it to restate $8.4 billion in earnings, while Freddie has said it understated profits from 2000 until 2002 by $5 billion in an attempt to reduce earnings volatility. Both companies have lobbied against the proposed legislation.