My honest reply, having built and restored cars, is that if yoou have to ask where you get a base vehicle from and the various parts to just make the car go and stop then you need more knowledge and experience first.
As a car builder I read a library of around 30 books on motor vehicle engineering and went to college to study the same, I then went to university and did a mechanical engineering degree and also took a welding qualification. I wasn't a professional, I just built for fun because I knew what I was letting myself in for.
If you want to have an electric car then your best bet, after playing with go karts and cycles, would be to get a perfectly sound and road worthy car with a blown engine and then convert just the drive to electric by removing the engine and replacing with a suitable motor. Then add a controller, batteries, charging and battery management system. Maybe add an electric power steering pump and electric vacuum pump for the brakes.
That makes the job manageable and the kart and cycle experience will safely introduce you to electric drive and battery management.
Have a look at
http://www.diyelectriccar.com/forums/ for more advice on getting parts for any electric conversion.