You can't solve a shortage of houses by discouraging people from building them. Canada is simply not building enough housing and has not been doing so for a long time. Your proposal would have a marginal effect at best and would in any case be only a temporary solution. People who buy second homes do so in places where there are generally few jobs. And people who buy houses as an investment need to rent them .. which is not necessarily a bad thing. The problem we have is that home prices have risen to such stratospheric heights primarily because of policies that discourage new development. The only way to fix that is to promote legislation that penalizes NIMBYism and encourages building in urban areas.