Wall Street has found a way to make money from the mortgage mess. Investment funds are buying billions of dollars' worth of home loans, discounted from the loans' original value. Then, in what might seem an act of charity, the funds are helping homeowners by reducing the size of the loans. But as part of these deals, the mortgages are being refinanced through lenders that work with government agencies like the Federal Housing Administration. This enables the funds to pocket sizable profits by reselling new, government-insured loans to other federal agencies, which then bundle the mortgages into securities for sale to investors. While homeowners save money, the arrangement shifts nearly all the risk for the loans to the federal government - and, ultimately, taxpayers - at a time when Americans are falling behind on their mortgage payments in record numbers. The trick is to persuade the homeowners to refinance those mortgages, by offering to reduce the amounts the homeowners owe. The profit comes when the refinancings reach more than the [amount] that the fund paid for the block of loans. The strategy has created an unusual alliance between Wall Street funds that specialize in troubled investments - the industry calls them vulture" funds - and American homeowners. But the transactions also add to the potential burden on government agencies, particularly the F.H.A., which has lately taken on an outsize role in the housing market and, some fear, may eventually need to be bailed out at taxpayer expense.