Not only do you have the lesbian stereotypes to have to deal with, but now you are getting hit with the same stereotypes us guys have to put up with, very high on the list is "We HAVE to pay to get laid" lol
As for the OP, I think just about everyone is misreading the OP, she did not say "once a week for at month" nor did she put any limit on the amount of sex, conversation, companionship, etc.
My answer to her would be, if I am to take her question literally, since she is going to have to be "on call" 24/7 it will be almost impossible to see many, if any other clients that month, depending on the guy's appetite of course. I think you should take whatever your typical months income is, lets say $10,000 just as a place to start and then add or subtract a premium based on how much you like this guy's company. If you really like him, it will hardly seem like work. OTOH, if you can barely tolerate him, a full month of him might seem like a thousand days.
Speaking strictly for myself, IF I were ever to enter into such an arrangement, "Unlimited" to me would mean sex "at least" two to three times a day each and every day so we are talking about fucking 75-100 times during at least the first month.
I did something like this many, many years ago, I hired an ex hooker to work for me in a legit job, with a "bonus" for every time we had sex, we fucked about twice a day,virtual every day for months, I finally had to fire her from the legit job, but we saw each other on and off for several more years.