Houston- A Houston couple accused of running one of the city’s largest prostitution rings conducted background checks on prospective customers — perusing their employment records and income levels — before allowing them to join the operation’s long list of clients, a police investigator says.

“If you didn’t have at least $300 a session, you couldn’t get in the door,” said Houston police Sgt. Mark Kilty.

According to court documents, some of the women met their clients at upscale hotels in the Galleria area and charged about $350 an hour.

While police are still trying to determine how large the operation was, Kilty said the client list totals more than 1,500 people.

Deborah L. Turbiville, 33, and her husband, Charles Fletcher Turbiville, 31, are charged with aggravated promotion of prostitution. They were arrested on March 10 and released after each posted $5,000 bail.

According to court records, the couple did “unlawfully and knowingly own, invest in, finance, control, supervise and manage a prostitution enterprise using more than one prostitute.”

Their client list includes professional athletes, doctors and lawyers, according to KHOU Channel 11.

“She probably had the biggest escort service in Houston,” Kilty told the Houston Chronicle.

He said the extensive background checks were conducted before the couple would allow clients access to the lavish Memorial Drive apartment where eight to 15 women worked.

The couple also accepted client referrals from trusted customers, stymieing the police investigation at first because it made it difficult for undercover officers to pose as clients.

Because of the extensive documentation collected, investigators plan on interviewing those named on the client list. They have not disclosed any of the names.

Police also are trying to find all of the women who are believed to have worked in the brothel.

“These are college girls, single moms and girls who were out of work,” Kilty said. “It was mostly a 50/50 mix of white and Hispanic women.”