Kenneth,
It is amazing just how much you and me have in common.
First of all, I am also 18, but I'm actually going to second year of University next year. I'm also in Canada
Secondly, I also had this problem convinving my parents that how much I had to pay for a bike.
Last year all I had was my brother's wal-mart bike. I didn't even dream of paying over a $1000 for a bike. But I rode it everywhere. I rode it for fun. I rode it for fitness. I didn't complain a whole lot. Looking back I cant belive just how much I rode that 50 lbs hunk of metal.
Then the Univesrstiy semester started and I had to put biking aside for a while. During this time I realized just how much I love biking and that's when I decided that I'm gonna spend good money on a good bike.
For over months I researched and researched. I told my parents about my decision and they were shocked! OVER A GRAND FOR A BIKE??? Are you kidding? What are you gonna be, a racer?
They just didn't undersand. But I was patient. Day by day I brought in biking into our conversation. I didn't act frustrated at all. One day we are all eating dinner and I would just talk about biking and how fun it is, how environmentally friendly... etc.
later on I patiently explained to them just what the difference between a road bike and a wal-mart bike. They understood.
My real purpose for a bike was training, but that's how I made my parents understand just how dear this was to me.
When I bought the bike, they were still a tad disappointed at my decision. They constantly would tell me: "Wow, for a little bit more than that you could have bought a car".
then I would say: "Sure, show me a car i can pedal and I will return this bike right now".
Now they see I go out for hours each day and just how much I love it, and they are happy for me. The other I told them I'm gonna spend the same amount I bought the bike for upgrades, and they weren't shocked at all. They understood.
So anyways, my advice would be to check out the buy and sell ads for a quality used bike. There are lot of them out there. If you get a new road bike for $1500, you have to realize how much tax comes on top of it and also the money you;ll need for various accessories and clothing and shoes... etc. They don't come cheap.
For about your budget right now you can find a good used road bike. Train with it for one year or two. Then move up from there.
Sometimes a humble begining is the best thing you could ask for.