Legal Question in Business Law in California

If you mean a prostitution ring, since that is illegal there is no license requirement as illegal activity can not be sanctioned as being allowed buy a governmental entity. I do not know if there are any that are not such.

You don't need a license to run the website, but I believe you do need one to run an escort service. As Mr. Shers notes, many "escort services" (and probably most, by a wide margin) are fronts for prostitution. Since prostitution is a crime, having an escort license will not insulate you from civil or criminal liability for any acts of prostitution in which the escorts engage.

Even if all you plan to do is run a website, there are a number of ways you can get yourself into serious legal trouble. Although you don't need a license to run such a site, you should work closely with a lawyer to ensure that you aren't doing anything illegal.