Living in Canada means snow, ice, salt as well as large climate fluctuations. We all know from our elementary school science classes how these affect different metals.
While salt has helped save many lives during icy periods, it also increases oxidation. Salt is used to melt ice/snow in winters but by doing so it creates salt water. As a result, the rusting process is sped up significantly, causing your car to rust much quicker than in warmer climates.
The unfortunate thing about rust is that it continually spreads until something is done to stop it. If you don’t catch the rust right away, chances are you’ll be paying way more to remove the rust than what you would’ve paid for rust proofing.
The decision is yours. You can either pay for rust proofing when you get your car and greatly decrease the chance of having it rust, or wait to get it removed when it occurs.