As far as I know permanent residents do not have to show a major income stream.
There have been several cases in the courts which may be of interest to you.
[edited] I might have misread the judgement [/edited]
Take a look here
http://legalref.judiciary.gov.hk/cgi-bin/lrs/search.pl and search for "permanent resident" and "income" and "dependant"
You'll see some test cases which have gone in both directions.