If cars were designed by architects...
Your car would be designed based on what kind of road you live next to. This process would take several years, even though there are already many cars on the street you live on. After your car is designed, your town government will have to approve it. Then your neighbors may complain and force you to redesign your car. When the design is finally finished, your car will be built from scratch. Parts will be sent to your garage, where the workers will then proceed to assemble your car. This will take 50% longer than you expected, and cost 100% more than expected.
The finished car will look nothing like some of the older cars, although it will run on the same engine. It will look very impressive from the front, less so on the side, and even less so on the back. This is because all parking is tail-in.
Every few years you will have to repaint your car, both on the outside and on the inside. Periodically you will reupholster your car. The car itself will last over a hundred years if properly maintained, though you may need to strengthen the frame by adding steel bars to the outside.
Eventually when you want to get a new car, you will have to dismantle the old one first. If you're lazy you can simply blow up the car.