The City of Minneapolis has a 10' wall height maximum so a car lift will work with some smaller autos. I just built a garage in Coon Rapids with 15' wall studs. You could stack a full size Ford f150 and a Chevrolet Suburban with no problem there.
Each city has different maximum wall height requirements so check with yours before you consider purchasing a car stacker or contact a Western Garage Builders representative to take care of it for you. Minneapolis 952-920-8888 St Paul 651-644-6900.