What do you think happens when housing supply increases at the cheapest level? Prices lower in general because private apartments don't get rented anymore at the price they're at, that makes condo prices lower because people stop buying instead of renting because it's now cheaper to rent and so on...

We were building affordable housing until the early 90s, prices have been increasing exponentially since then. The reason you've got foreigners buying here is because prices go up, it's speculation, but it's been proven many times that stopping foreigners from buying just means locals get more opportunity to do exactly the same thing. Anyway it's not as if rich Chinese buying 5m$ houses in Vancouver were the reason why people can't find affordable housing in Sudbury.

Supply and demand. That's it. Flood the market with more affordable housing than is required (and that's inaccessible to speculators!) and regular people will get access to a cheap roof and speculation will not be profitable.