$300 a month! no way jose!
I can only think of 3 places.
CWB has a hostel which is $95 HKD a night it is grotty though no wifi and the dorms are packed 3-4 beds high, it was run by a Mr Lee. Dorms though. $11US a night = $330 US total
ChungKing Mansions Block A 3rd floor has Taiwan hotel which is $120HKD a night + $100 deposit, room is basic air con TV, ensuite one narrow bed + free WIFI If you stay long term more than a week the silver haired woman from Taipei (or if you lie and say you are from say Hualien (but be careful she asks probing questions) she will give you a $15 discount. Private rooms.$14 US a night
There are similar hostels and hotels in Mongkok but they are disgusting and cramped, NEVER stay in a NT hotel though they are horrid. = $420 US a month
But Hong Kong is Hong Kong and there are places to suit each and every budget, for $15o you can stay in Sham Shui Po for $200 a month (gone up since the report)
In a cage home
http://edition.cnn.com/2009/WORL ... ge.homes/index.html
However they may not want to rent it to you for such a short time, but simply around that budget there is nothing, if I were in HK you could stay on me sofa.
Out of morbid curiosity I am looking to stay in one of those SSP books as research for my 5th book (my editor was moved by a scene I portrayed about the cage homes in SSP in my 3rd novel and thus I thought I might attempt to do what Orwell did in Down and out in Paris and London and go see for myself what it is like). And write my 5th book on this subject.