The truth is that you can really ask for whatever you feel your time is worth. I don't say this lightly at all, I'm dead serious. Here's a little secret: no matter what rates you ask for as an escort, there are gentlemen out there who are more than willing to pay it in exchange for your time. So never sell yourself short, so to speak.
If you're still feeling unsure, the most obvious thing to do is take a peek at other VIP escort ads in your area. If you are worried about overcharging, try seeing what other women your age (with similar features are asking for. This should give you some idea of what the average rate is in whatever city you live in. Los Angeles and New York might command higher rates than Richmond, VA.
Keep in mind that you can always raise your rates later too, perhaps after you've been reviewed a few times and word spreads of your services. Just keep in mind that it's nice to continue seeing your regular clients at the same rate you have been charging them, since many will not be able to stay clients when rates go up by a significant amount.
It's oftentimes a smarter business move to keep a loyal and returning customer, even if you don't make as much from seeing them on a per-visit basis. Having some stability is important too, and it's always a good idea to have a few clients who you can count on.
To maximize your potential and diversify your client base, it's always a good idea to offer rates for several different blocks of time. It can be as short as fifteen minute sessions or as long as an overnight meeting. This ensures you won't get burnt out on encounters that are too long or too short. Just establish a fair rate for each time block and stick to it for the most part.
Don't be afraid to charge what you and your time are worth.