Sorry, no. Quite frankly, this is still an illegal industry. It needs to be kept as much in the shadows as possible. Just my opinion

What?  That's crazy.  Agree with what Bond said.  No one in their right mind should get involved with this.

The more "REAL" he makes this, the more real the consequential LE action will be.

...the passage of FOSTA/SESTA.  Humanizing the men and women would be a first step toward the repeal of FOSTA/SESTA.

In LA, similar to the "within six steps of Kevin Bacon game", the same goes with escorts.  Pretty much everyone knows someone who, or knows someone who knows someone who.. so it cannot be difficult to find someone to talk about the sex business.  I've become "friends" with girls and if you want to ask them a question they will tell you.  So tell your wanna be screen writer to conduct interviews the old fashioned, but fun way.  E.g. hire a girl a few times, then interview while getting a bj!  
P.S.  At least 1/3 of the girls I've met are actresses/musicians, make up artists, etc.  So if the screen writer is in the business, he has easy access to people to interview.

And therefore you can receive and send PMs.

Out here thats synonymous with the old joke beginning “A guy walks into a bar with a monkey...”.  I myself have been working on an operetta about the hobby for years and you are all in it, names withheld to protect the not so innocent.  I did my research the old fashioned way - I lived the experience, which Hemingway said was the only way to write.    

Besides, it doesn’t take much imagination to figure out that the ladies we love so much in this game we play are just like everyone else on the planet - saints and sinners, angels and demons.  Some pure of soul and heart some toxic as Chernobyl.  A whole lot of college girls aspiring to get on with their lives and quite a few lifers who profess no desire to do anything else.  I’ve met nurses and lawyers, housewives and actresses,  models and mongrels.

If your friend wants to talk to escorts, he should make a date or three.  After all data is as much of a commodity these days as everything else.  He already has his reference in order and he doesn’t have to sex if he doesn’t want it.  We’re all just trying to make a living here.