my mom and ex-step dad used to run a car importation business that imported cars from the US to canada and vice-versa. basically there is a ton of paperwork involved with agencies like DOT, the MTO, EPA, there's border hassles, registration is a pain, of course the speedometer needs to be converted, of course the car must meet applicable EPA emissions requirements. and of course all the middlemen along the way want their cut of $...
they did all this like a well oiled machine since they did it in volume, but it takes a bit of manpower. try to look for a registered importer (RI) in your area.