I think it is associated with Touch of Class Kingston. I am led to believe (by a former TOC girl) that prior to being able to use the Gentleman's Club, you have to have an established relationship with one of the girls from TOC. Then, you can take her for an overnighter at the club in Gan, just you and her (is my understanding); it's not a brothel or anything like that - just an empty house that you can take one of their girls to for an overnighter.
But my information is at least a year old, so things may have changed. Why not call the posted number and find out.