Eh ?  Read line number 1, check the market conditions. This is a sample calculation based on someone's outlook over a 5 year period.

1) Over the last 30 years, average house price has increased by 5.65% per year in Canada. Incidentally stock market long term average is also 5-6% a year. It is not 10-20%.

2) Historically the house price to income ratio was 3.41. Now the house price to income ratio is 7.62 in Toronto, and 5.4 in Canada nationally. 

It has been shown that people's mortgage payments are similar to what they were in 1980s. However, due to the interest rates having stayed persistently low, they are carrying much higher total debt, and smaller portion of interest.

That means that if rates rise, all that debt is going to become unsustainable, and the market will have to correct.

The question is what market event will cause rates to rise, and with the US Federal Reserve outlook, rate rises look to be more likely in the next year or two.