As an enthusiast, I would never own a second hand Tesla. They have terrible build quality and you just see too many rollers (major power train or battery issues). 10 year old cars mechanically totaled is the opposite of an eco friendly vehicle.
I read the biography of him and yes, it's molded in one piece (or was at the time of the book from memory) it was inspired by the bottom of a toy car. The issue of water ingress was apparently brought up but he didn't think it would be an issue.