Maybe the attached will give you some answers.

 
I've never paid a deposit but some do. I've never seen a deposit required just for out call -- typically just a higher rate than the in call rate.  But then I've never don't out call except when I was out of country so....

I started requiring payment upfront if ive never met you before. It ensures that i wont be screwed or have my time wasted by showing up to someone’s house and them not opening the door. But thats just my personal preference