Hi Bro
Please use the search function, as lot of your questions have already been asked by previous newbies. But, just to make sure you get your answer fast, overnight fee for a typical HG (hotel girl) is around 3x her going rate, and it usually starts after 11PM or 12 AM to 8-9 AM. Of course you can always SMS papasan, they are better at reading writing English than conversational English.
I am not sure about the whole day rate, but it could be in the neighborhood of ~5K for a typical HG.
Have fun in HK, and don't forget to post a review when you are done.