OK bro here it is: you're going insane
As a young guy, don't sweat it, you're a prime target. Just go out to to meet girls (e.g. Wanchai) and you'll be hard put to STOP them coming home with you ... no money required ...
... or pick them up in the street if you like, there's nothing illegal about sex, nor even sex-for-money ... just make sure they're old enough, and be straightforward about what you're looking for. As an 'outsider' (don't know if you look Chinese or not) you have an edge in being able to talk about taboo subjects without giving as much offense as a local would cause.
Only thing for you to check into is what are the rules where you're staying? If it's a guest-house, you're probably paying per-person, and you'll have to pay for the girl to stay over. If it's a hotel proper, you're paying per room, and you should be able to bring a guest back.
If you really do want to spend your money, best place to start is the Newbies guide, it's pretty thorough
http://forum.sex141.com/eforum/v ... &extra=page%3D1
Apropos I was looking for mandingo's old "newcomers guide" - I found it excellent when I was starting myself, and the narrative style made it very accessible - anyone know where it is?