I knew a couple of people that were going to import a vehicle from the USA and changed their mind.
The amount of tax that you will pay on the vehicle will be decided on the value that government gives it, and I think if it has a/c it will have a additional tax.
You may have to change things on the car also, like bumpers
(Canada has different regulations, I not sure if it will require day time running lights.)
The car will have to have a inspection to be registered in Canada, that is different from the safety inspection.
I think you have different rules in Quebec than Ontario
The best thing to do is to contact the Ministry of Transport and ask them directly!
You may want to get in touch with a company in the USA that can check for liens on US vehicles.
(You could be paying a lot more than you think if it has a lien on it!!)
Hopefully the person you are dealing with is honest, it is not easy to resolve things if the car has problems.
I think it is best to buy locally with a large purchase like a vehicle.