Respuesta: In BsAs streets, must we always pay first ...?
I have found that typically most girls will ask you to pay first.
After being with them a couple times, then they begin to trust you and are much less likely to demand payment up front.
I know some guys are horribly against this, but in my experience, i've simply found that if you pay up front then the girl is not going to be worried about getting paid. (You can guarantee that either her, or a friend of hers or she has heard stories about being ripped off in the past).
If you want to ensure good service, talk a bit about what that means to you (i find jokingly is good), then let her know that you'll tip her at the end of the session if you're happy with the service. Some guys are against this as well, but I typically find a small tip gives me better better service.
good luck