Struggling developer Harry Macklowe could sell up to 50 percent of Macklowe Properties, in an effort to save his real estate empire from creditors. U.S. and foreign investors are reportedly being lined up, as Macklowe’s son Billy, president of Macklowe Properties, leads negotiations. Harry Macklowe has been in trouble since his short-term debt became overdue. In a highly-leveraged deal, Macklowe spent $7 billion on seven Midtown buildings last year and used the GM Building as collateral. Macklowe has been unable to sell the GM Building for at least $3 billion, the minimum price he wanted.