Try with some basic modelling first, before creating a whole car. It's a lot of work. LJ74 made a good tutorial on this also this: https://documentation.beamng.com/vehicle_system/index.html good luck
Many have tried and many have failed. If you have NO experience with moddeling, 99% sure i wont see your car finished.
maybe a hundred or so at most. if you enjoy working with any sort of 3d modelling software, and have spare time, there's no reason why you would be unable to make something.