Well, with emails, questions I would ask would be:
How often is email allowed?
Will you always respond? (Or only if I request a response?)

If so, in what time frame will you respond? Do you respond on weekends/after work hours?

With calls, you could ask how much advance notice is needed and what times he's willing to do phone calls--like could you request a call at 4 pm and talk to him that night? Would it be the next day? Is it only during his work hours?

I know in another post, you were wondering about whether he takes your insurance and, if there's a problem, whether he'd offer a sliding scale (and what that amount is). So that could be something to ask, too, though you wouldn't want to take up the whole time with him, say, looking up your insurance.

Do you know how often he's willing to have sessions, whether it's the same frequency as L?