Glass will always be expensive. It's just physics. You can only bend light so much with mirrors and optics before distortion comes into play.
I used to work for a real estate photography company (and do some freelance stuff occasionally) and have a 12-24mm wide-angle zoom. Your cheapest bet would be a Tokina 12-24mm which used is approximately $400 CAD on private classifieds.
Pair that with a cheap body like a Nikon D40 <$300 and that's the easiest.