So, as a learning thing, you can only be charged if the police can prove you showed up with the irrefutable intent to purchase sex acts and that the burden of proof is quite high requiring first-hand observation / interaction and not hear-say allegations.
In other words, the police standing outside one of the known condo buildings means they can't prove intent. Standing outside one of the SPs units inside the condo building is not good enough to prove intent.
Really what needs to happen is for a police officer to receive a request for a sex act (online, text, email), you go over to the address, enter the residence (condo, house, whatever), you pull out cash and say something incriminating like, "here is the money for that sex act we discussed" or for the undercover police officer to request the money for the sex act you two discussed.
I guess what I am seeking confirmation on is the burden of proof for police is quite high as described above. Also, it sounds like independents could be more suspect at this stage. Established agencies with established SPs should be fine unless they are compromised somehow.
I assume if the police suspect something is going on in a specific condo building AND a specific condo unit / residence, they could get a warrant? Possibly catch people in the act, but they would lack that first-hand proof that the two or more people smashing aren't doing so because they got paid.
Bonus question: I assume if you ask: "are you a cop?" they have to answer truthfully, otherwise it could be entrapment. I think entrapment is a little grey in terms of legal permeability.