I think people who aren't very familiar with immigration simply don't know that permenant residency exists (what the US calls a green card, since pop culture makes that better known). When most people immigrate to Canada, they get permenant residency. Citizenship doesn't come till much later and many don't get it because it's just not necessary and some countries don't allow dual citizenship, so getting Canadian citizenship would mean giving up your other citizenship.

So yeah, permanent residency is likely the most reasonable requirement. There's also people with longer term temporary residency, like people on student visas or temporary foreign worker programs, but I don't think it makes sense to own housing as a temporary resident. They can rent, as many already do.