If you buy a vehicle that is made in North America (Mexico, US or Canada) it will be duty free. But you will have to pay taxes, both provincial and federal. There will be also a fee can't remember what it is for but its something like 200 bucks. Then you will need to have it inspected in your province and bring the vehicle up to Canadian standard (ie: driving lights), which is done at Canadian Tire stores nationwide.
You will also need the title of the vehicle, which must be clear and you must present to the US border for clearance, take notice it take THREE DAYS to clear before you can bring the vehicle to Canada. Unless you can get your hands on the title before getting the vehicle and getting it cleared to get the ball rolling so you don't have to wait three days to get the vehicle across. Its a PITA but sometimes its worth it if you got a good deal.