I beg to differ here. If you can only have one lens I think you should be going for a zoom lens. It may also depend on the subject matter you intend to shoot though.

Yes the lens Iggy is saying is excellent, and would be a great lens to have, I think it is better to have a versatile zoom if it is going to be your only lens.

I don't know the going rates in Canada, but you could be lucky enough to pick up a Canon EFS 18-200mm zoom second hand. This is a very good, very versatile lenses. Be aware though that it wont be any good if you decide to upgrade to a full frame camera (and for that reason a lot of people sell them quite cheap when they upgrade to full frame cameras)

Just another take on this.