NEW YORK (CNNMoney.com) -- Drowning in a mortgage you can't afford? Whether or not you get a new one will be decided by someone you've probably never met at a company whose role is barely visible: the mortgage servicer.

Nationwide, as home prices plummet and foreclosures rise, thousands of Americans at risk of losing their home are trying to work out new loans. In Washington, Congress is debating a massive rescue aimed at 500,000 people.

And all of the efforts to keep people in their homes run through the mortgage servicers, who are responsible for deciding which troubled borrowers will get more affordable mortgages.

The problem is that servicers are being overrun by the foreclosure crisis: They were set up to process payments, not do loan workouts on a massive scale. As such, they lack the financial incentive to help homeowners workout new loans.

"The economics don't make sense for the servicers to do a workout," said Bruce Marks, chief executive of Neighborhood Assistance Corporation of America, a foreclosure prevention counseling group. "They're not set up to do restructuring."

Servicers collect payments and manage loans. Some, like Countrywide Financial or Wells Fargo, are also lenders; others are only in the business of servicing loans. All servicers are paid a piece of the monthly mortgage payment and funnel the rest to investors, such as hedge funds, that hold securities backed by mortgages.