Yes, you can live okay on US$6000 per month. As PC, GH, RP, etc will confirm, that's about what I get paid. If you want the big money, become an engineer...
Impossible to answer the question about housing as it is so dependant on the area you live and the size of your house/apartment. I suggest you look at this web site:
http://hongkong.asiaxpat.com/forums/default.asp?id=1
There is a lot of info there about living costs. You should do a search of the site because any questions you may have will have been answered before.
Dunno about the policy regarding locals/expats and housing allowances.