A Markham man pleaded guilty Wednesday to prostituting a 14-year-old girl and having sexual relations with her even though he knew she was underage.

Hon Sing Tsui, known as Joe Doa in the escort world, appeared in a Newmarket courtroom where he pleaded guilty to living off the avails of a person under 18, sexual interference and failing to comply with an undertaking and bail conditions.

The court heard Wednesday that a deal with the Crown will likely see more than 30 other charges against Tsui withdrawn.

The 30-year-old is expected back in court on Aug. 25 for sentencing.

The investigation into Tsui was sparked in April 2010 when police responded to an unrelated call at a Clegg Road condominium in Markham. When York Regional Police officers arrived, they found a bawdy house operating out of one of the units.

Days later, police received a tip about a teen who had been working at the agency for two years, beginning when she was 14 years old.

The girl told police she had answered an ad that Tsui posted on Yorkbbs.ca looking for women to work at his escort agency. She said the two chatted over MSN before meeting in person.

The girl said Tsui had sex with her even though he knew she was just 14, police told CTV Toronto's Tamara Cherry.

When the teen began working for Tsui, she serviced clients from hotel rooms across York Region before moving to the Clegg Road condo near Warden Avenue and Highway 7.

Const. Rebecca Boyd, a York Regional Police spokesperson, said Wednesday the case shows the dangers of young people getting involved with strangers online.

Pimps know what to tell vulnerable teen girls, she said.

"They think that sometimes the world is glamorous when it comes to escort agencies and living a high lifestyle. It's not necessarily the case," Boyd said of the victims.

Pimping is not an isolated problem in the GTA. Tsui was one of three accused pimps who appeared in Newmarket court on Wednesday.

With a report from CTV Toronto's Tamara Cherry