wow didn't expect such a response to the turn off posts .. but guess to be expected.   so what is your number 1 thing that turns you on / you enjoy about the hobby .....   for me, bottom line is convenience.   (the sex is a given)

Beyond the obvious, which is her looks, I would say it's her vibe. One provider I saw had a very creative and fun website. Nothing about it was vanilla. I immidiately got the sense she was fun. She was from out of town and I wanted to see her for quite some time. When I learned she was travelling to my city, I booked her a good 3 weeks in advance. And, when I met her, I struck gold. She was by far the funnest provider I have ever been with.

Must  I  really  choose  only  one?
Not  necessarily  in  this  order:

Something about women who like it in the can. You have to be adventurous for that. Always my favorite kind of woman.

I don't dress like a slob when I see a girl and I expect her to look good too.  You can tell when she's tired, doesn't care.  But when she's looking her best for me?  That's always gonna make me happy.

The ones who realize it isn’t about them it’s about the client . You would think that’s the norm lol

a fantastic photo has made me pull the trigger more than once, and I’ve never had any regrets from it.

Toned, sexy legs that the lady moisturizes often and that are silky soft. Nothing gets me going more than a great pair of gams and a woman who isn't afraid to show them off.  
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That's the physical though. Personality wise, girls who are more demur, sweet and submissive is something that I am wildly attracted to. There isn't anything more sexy, for me, than a young, gorgeous woman submitting to me in the bedroom. It is just as thrilling now as it was 15+ years ago when I first started.

The "anticipation" of meeting a new gal.  The image I know from her website or ad is hopefully accurate as the door swings open.  

And she doesn't have to be all that on the looks. Double OMG D's on a thin/slim girl...stick a fork in me, I'm done.