David G. Marshall CEO of Amerimar Realty in Philadelphia has made a career of seeking out bitter lemons and turning them into sweet -- and profitable -- lemonade. Through the years he has taken over distressed properties -- such as The Rittenhouse in Philadelphia Pier 39 in San Francisco and Denver Place in Colorado -- and made them into successful enterprises. Marshall recently went to Shanghai as part of the Wharton Fellows program and came to the conclusion that what is happening in Chinese real estate ought to be a wake-up call for the U.S. market. Knowledge at Wharton spoke to Marshall about his visit to China and other issues.