Two weeks after pulling off one of the most expensive and complex real estate deals in recent years, investor Joe Chetrit has taken a big step forward in arranging the nearly $1 billion worth of debt he needs to close the transaction. Mr. Chetrit, a prolific and successful landlord and developer in the city, is in talks to have the real estate investment trust SL Green Realty Corp. provide between $800 million and $900 million of financing for his purchase of the 36-story Sony Building, according to sources. SL Green, the city's largest commercial landlord, would in turn sell off the senior portion of the debt to a major bank it would partner with in the deal. It would keep the rest, up to $300 million, as mezzanine financing on its own balance sheet. SL Green would also have the option of carving the mezzanine debt into different tranches and selling it off to a host of buyers. As the real estate market has recovered from the recession, mezzanine lending, which suffered heavy loses during the downturn as values plummeted, has been rebooted as lenders have searched for better returns at a time of very low interest rates. "There is a lot of interest in mezz pieces," said Shawn Rosenthal, a mortgage broker at Ackman Ziff who is not involved in the Sony Building's financing and had no direct knowledge of that deal. "Overall yields are so low, lenders see there are opportunities for them to be a little higher in the leverage stack and get a better risk adjusted return." Last May, Mr. Rosenthal arranged the $400 million refinancing of 452 Fifth Ave., a 30-story, 650,000-square-foot office building next to Bryant Park. About $100 million of that debt was sold by the loan's originator, JPMorgan Chase & Co., as mezzanine debt to MetLife. The deal to finance the Sony Building, at 550 Madison Ave., makes particular sense for SL Green, which has used mezzanine positions to foreclose on real estate in the past, including the downtown office tower 100 Church St. SL Green was rumored to be among a long list of large property owners in the city interested in owning the 700,000-square-foot Sony Building. "It sounds like the dollar value of the mezzanine loan would be a price that SL Green would love to own the building for," Mr. Rosenthal said. Mr. Chetrit's aggressive projections of future profits and the complex debt structure he is laying to provide a bridge to that rosy future have drawn some experts to compare his deal to the ambitious and risky transactions of the pre-recession boom. Mr. Chetrit wants to convert the bulk of the building into luxury condominiums that would fetch prices of $4,000 per square foot and higher. He also would sell or lease a portion of the building to a high-end hotel operator and improve the building's retail space.