Working in USA and thinking of buying a car to take back

I am currently working in America. I've been working on a TN visa for about 2 1/2 years. I have an apartment in NY which I use during the week and then go back home to Toronto on weekends. My visa is sponsored by an American company so I pay U.S. taxes and then I also submit Canadian taxes. Given that I'm an American resident (although not a permanent resident), if I buy a car in the states will I incur a cost when I move back to Canada permanently and take the car with me?

Not if you keep it long enough in the US (at least one year). As least as far as duty and GST goes, you'll have to re-register it, transfer the title and meet the import requirements: www.riv.ca which usually means you have to fiddle with the headlights.

If you can't keep it in the US for one year, the best idea is to buy a car made in N America as it will be exempt from duty under NAFTA. But you may get hit with sales tax.

A few years back I imported a motorcycle and did not have to pay any duty or taxes. I had to prove to customs that I had been in the US for 2 years, which I did with old TN Visa's, and I had to keep the bike in my name for one year after importing. I found real easy to just visit a canadian customs office away from the border with the vehicle.