Greene says he paid the fee himself. But in November, Greene, facing a federal obscenity charge, asked a state court for a public defender because he didn't have the money to pay for a lawyer.
"We want to see how he came up with the money," SLED director Reggie Lloyd told the State.
Greene's public defender said last week that he has been told to stand down after receiving a letter from a private attorney hired by Greene. The case is still pending.
SLED will use a new law, signed last week by Gov. Mark Sanford, that allows SLED to subpoena financial institutions for basic information about their customers.
SLED was asked to investigate by Republican state Rep. Chip Limehouse. Limehouse contends that if Greene is not poor enough to require a public defender, he should refund the taxpayers for his legal services.