This is something that rears its ugly head from time to time. The email I've just received in my inbox reminds me that I should put a warning up for newer escorts who have yet to encounter these types of emails. They target lots of people but in particular escorts.

Beware of emails that promise you long bookings. They're scammers from Nigeria.
They write to you with English-sounding names and promise to pay you over the odds on your own rate for overnight, 1, 2 and 3 night bookings. They say that they have to send you a cheque for not only your rate but extra, usually a lot extra.
Then what happens is that they ask you to send the extra money back to them. Then the cheque doesn't clear and you're left with a big hole in your bank account which you have to pay.
This scam has been around for a long time. Newbie escorts please beware, I've read that a few ladies have fallen for this:

Hello,
 
  I will be coming down there very soon for a Conference which will be taking place beside your location. i shall keep you update as soon as the date is confirmed; please i will like to know your best offer as i will be having you for the 3 hours and you will also get back to me with your current location through your e-mail address and best offer per night and your contact phone number so as to continue with you for upfront payment as i like your ads. Here is my e-mailaddress.jerrysmith072001@yahoo.com .i love using this prepaid mail account for the maximum security it entails.
 
 I await your quick response asap.
Jerry