Turner Broadcasting System Inc. is considering selling its headquarters, CNN Center, and other Atlanta real estate to help pay off its enormous debt, Chairman Ted Turner says. "We are fairly early into looking at exactly how to do it, but we know that what we've got is worth a lot of money," Turner said. He said the company had talked with several possible buyers, but he declined to identify them. In addition to CNN Center, TBS' Atlanta real estate holdings include about 35 acres near the Georgia Tech campus. The corporation has $73 million in real estate debt, $150 million in notes from acquisition of the MGM library in 1986 and other debt of $1.3 billion.