I've just had the time to glance over this discussion briefly. It looks really interesting and I can't wait to spend more time reading it in-depth and thinking about the comments.
Until then, I'd like to offer one clarification (I see someone made an attempt already but didn't get it quite right): Our system in Canada now is that you require 20% down for investment properties, and 5% down for owner-occupied properties (with the CMHC insurance). Those down payments cannot come from loans or other financing. They must be your own cash or a non-repayable gift.
I guess the thinking is that requiring 20% down for investment properties increases the stakes for investors and reduces some of the rampant speculation that causes bubbles. Lowering the bar to 5% (with insurance) for owner-occupied properties means that people can still afford to buy a home.


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. As Pogo said, "we have met the enemy, and he is us."