This plan is asking the new condo buyers to subsidize the rental units. The developers will just pass these costs on to the buyers of the new units. Just as if the cost of drywall rose then they pass that on to the end buyer. Somebody always has to pay.

No  condo building gets the financing from the banks until a certain number of units are pre-sold. This reduces the risk to the financial institutions. This was put in place by the ,banks and govenment, thanks to the 1981 collapse of the market which left a LOT of FINISHED product on the market. This drove the prices lower and people simply walked away from the projects. These rules were put in place so we wouldn't repeat that again. This is exactly one of the things that happened in the United States in 2008 that helped melt their markets.

Now developers have to own the land 100% without any financing before they get the conditional approval for financing. 

Gregor is using Seattle and SFO as models that didn't prevent rising rents.