There seems to be a fascination with this among some of us.  I don't get it, but I don't judge.  The point is, you really can have no idea how many guys any girl sees in a day or a week.  Don't even bother to try.  Just see someone you find attractive.  Most of the high volume girls are on Backpage and you won't find them on this site.  Finally, as long as you engage in protected sex it's highly unlikely you need to worry about getting HIV, or any other STD.  That said, it's not impossible.  If that's a deal-breaker for you, perhaps you should find another sport.

Of course.  Anybody who does "this thing" thinks about it.  It's always a calculated risk.  But then so is having sex with anybody.  You could meet a girl in a bar and have the same odds.  You could also get hit by a bus crossing the street.

I'd say you're much more at risk for an STD than you are AIDS, but, hey, it's always a risk.

Either hobby and accepts the risks (and do all you can to protect yourself) or don't hobby

Well hobbing with escorts has risks just like driving a car or flying in a plane. But you don't stop travelling because a car will get into an accident. When you see different escorts you are taking a risk the same way they are. Play safe, read reviews and enjoy yourself. If you are too afraid find another watch pornography or something.