I?m considering buying a condominium in either Hong Kong or Shanghai,
but I?m wondering if the timing is right and would like to look back
at monthly (or failing that, at least quarterly) data over the last 15
years to see what residential real estate prices have been doing. I
have a vague feel for what prices have been doing in Tokyo, Montreal,
and Monaco during this period, and it would be very useful if there
were data series on the Internet that would allow me to chart the data
for different cities, combining prices for say Tokyo and Hong Kong to
see what they?ve been doing.

I would hope that this data would be in the public domain and that
there would be sites allowing users to look up the data for free in
the same way that Oanda.com and other sites allow users to look up and
chart historical forex data for all currencies for free.

If a free site does not exist, I would want to know what are the sites
that offer the most comprehensive data (including the most cities,
with the historical data going furthest back in time) for the lowest
price.

Just a free comment:

Personally, I doubt that using the historical data you ask for is the
best way to make a decision about where to buy a condominium in China.
 The economic development in China and the unique political situation
in Hongkong have changed too much in recent years for trends of the
past to have much bearing.
For example, there has obviously been a housing construction boom in
Shanghai in recent years.  I expect that prices have risen with the
demand, but this may have led (or may lead) to too much construction
and a fall in prices.  The political situation in China is such that
there could be controls on prices or restrictions on further
contruction or foreign ownership, any of which could influence the
future value of a condo.

I believe better sources of information would be a selection of
analyses of the present real estate markets, from which you could make
a decision.

Good luck.