General overview / cross-section (easier stuff)
Bars in the backpacker district with girls, cost 1. 5 million -- all near where Bui Vien meets Do Quang Do street. Expensive and very mixed in quality, but if you look hard you might find a good one. Someone said more girls come late (midnight and after) but I haven't checked that late.
Apocalypse Now disco on Thi Sach street. Price ranges from girl to girl but 1. 5ST is possible. Sharpen your bargaining skills.
Full service massage parlors in District 10 at 1. 3 million - 815 LE Hong Phong street is probably best one -- Hai Yen is the name. Others near there. Haven't tried myself yet but have heard good things. I hear it's busiest 5-11, so just before that probably best selection.
Nguyen Phi Khanh street in upper district 1 with lots of 'hot toc' salons offering BJ at 400 -- tried this recently, pretty good. Start at Vo Thi Sau and walk up this street, they're about half-way to the next big street. 8-10 of them.
Go 2 bar after about 2 am, upstairs, dance floor area. Many working girls come at that time (from Apocalypse and elsewhere). Not sure of current price but probably 1. 5 million or so. Corner of Bui Vien and De Tham street, backpacker district.
As you see, there's some very different types of venues here. Obviously there is more than this out there, but this is a pretty good place to pick something to start out with, for new people here.