In the case of a massage parlor, tanning salon, aramotherapy salon, etc., tt's very simple, the cops obtain a warrant to permit them to operate the place.  The female cops try to get you to solict them for sex and you are busted.  The process you, scare you, etc.  Pretty much it is as you have seen it on tv.

It is very rare that the DA actually prosecutes.  The arrests are the product of entrapment; albeit may be technically legal; mostly not.  The goal is to stop the customer flow to the place.  The DA does not want the typical dialogue from the arrest before a jury as it can be quite steamy, or coy, or really verrrrrrrrrry funny.  Actually, it is always funny, sometimes pathetic -- both from LE and the john.

Basically, don't say much when you are with the girl, just let your hands wander and try to cop a feel before the cop stops your exploration!