Its not illegal if you know what to say
Tell a "pro" that you would like to hire her if:
-you can have other people watch
-video tape the performance and sell the tape over the internet
This is why porn stars don't get arrested.
CALIFORNIA PENAL CODE
653.20.
(a) "Commit prostitution" means to engage in sexual conduct for
money or other consideration, but does not include sexual conduct
engaged in as a part of any stage performance, play, or other
entertainment open to the public.
Your state or country may be different.