Sounds like you may have heard horror stories! I think it won't be so bad ;-) With good management of the rent, as Shri says, you'll likely be able to meet your goal.
Certainly rent factors into the equation in a big way- as any money I put into rent is money I don't put into my pocket. Don't want to live in a dump, though, or I'll get depressed.
Where will you work on Kowloon side? Hong Kong not good for a young single guy? S'pose it depends on what you are looking for. But, I haven't heard that. In fact, I think it may be a bit more challenging for a not so young guy who's here on his own ;-)
My new office will be in Lai Chi Kok on the Tsuen Wan line. Ideally living not far from that line would be good strategy.
What I heard about the nightlife was that it's very divided between the foreigner and the locals- not much intermingling. The same could be said of Bangkok, however, if only because foreigners tend to congregate together and don't venture out into the Thai areas. Will have to see for myself...
I would say you can eat for under 100 HKD easily...or can splurge on dinner for two at 2000. Lots of choices. I regularly have lunch in Kwun Tong (where I work) for $32.
Sounds like overall things aren't as bad as I imagined... I was imagining living in a tiny box eating nothing but noodles every day to try and meet my savings goals. Will have to try and not go crazy in the nightlife areas... If HK is anything like Tokyo one can blow through a lot of cash in an evening....