Freddie Mac’s net worth has fallen below zero as the company seeks more federal aid and looks for a new CEO.

In its recently reported fourth quarter and year-end 2008 results, the company posted a net loss of nearly $50.1 billion for 2008, with $24 billion in losses occurring in the fourth quarter. The fourth quarter losses pushed the company’s net worth—or the difference between assets and liabilities—to a negative $30.6 billion.

So Freddie Mac’s conservator, the Federal Housing Finance Agency (FHFA), has submitted a request to the Treasury Department for additional funding of $30.8 billion, which Freddie Mac expects to receive by the end of March. That’s more than twice the $13.8 billion that Freddie Mac received from the Treasury Department in November.

In announcing the grim results, the company also named John Koskinen interim CEO after David Moffett, who was appointed CEO last September, resigned from that post in February. Koskinen, a former deputy mayor of Washington D.C., has a lot of experience in restructuring troubled enterprises: As CEO of the Palmieri Co., he led the restructuring efforts of the Teamsters Pension Fund, Levitt and Sons, and Penn Central.

Though the company continues to provide liquidity to the multifamily sector, Freddie Mac’s troubles have had big ramifications on the affordable multifamily housing market. The company abandoned the low-income housing tax credit market last year, and FHFA now reports that Freddie Mac missed its affordable housing goals in 2008. FHFA has responsibility for setting and enforcing those goals, once the domain of the Department of Housing and Urban Development (HUD).

“For 2008, it now looks like they missed almost all of the goals set by HUD,” said James Lockhart, FHFA’s director, at a housing conference March 13. “It seems likely that the income-based affordable housing goals for 2009 will look more like the goals HUD set in 2004 and 2005.”

As the single-family housing crisis continues to deepen—Freddie Mac now owns about 30,000 homes—the company is taking steps to minimize the impact of the foreclosure process. Freddie Mac launched a “rent-to-own” leasing program earlier this year that allows homeowners to rent the properties on a month-to-month basis after foreclosure. Those who were renting homes that have since been foreclosed can also continue to rent on a month-to-month basis under the program.