The HK housing index is at
www.rvd.gov.hk/en/doc/statistics/rvd1_2.pdf .
Applying the CX formula gives you about $23k/mo these days, which is more than enough to rent a nice 3 bedroom flat in Discovery Bay, but low if you plan on living in the more trendy areas of the island. DB is easily the easiest place for an expat couple with kids to live, but like anywhere else in HK, it has its pros and cons. Have a look at:
www.geoexpat.com and
www.dbfleamarket.com for more background.
In general, you'll be able to afford a nicer place to rent than you could buy, since if you buy, you'll be liable for a myriad of other expenses, such as maintenance and various taxes.
Just as in North America, you can get away with a high ratio mortgage (5% down) but you will be liable for additional insurance fees for the bank.
The housing market is in somewhat of a decline right now, with US interest rates on the rise, so we decided to hold off on a purchase. Most leases are 2 years, but both landlord and tenant have the option to withdraw after a year under current rules.
For a good overview of what the money can get you, have a look at:
http://www.gohome.com.hk/english/