What I said applies to all businesses. every last one. And, yes, even yours.
Unless you are planning on building $20k paperweights, or selling $20k plus time and other costs into a vehicle, only to sell it for $5k, anyway. I've seen many such "business models" go awry... again, even if they have face merit, the investors fall short if they lack planning. For example, you're not likely to set up "deals with suppliers" when you are only buying 1-6 parts per year.
I'm really not trying to be rude, I'm just pointing out some things. I'm not going to sugarcoat it, though, as doing so might make you think that such considerations are optional.
I'll give you a head start. One "acid test" for such ideas (though obviously not 100% reliable) is a simple question: If you were offered what you are planning to offer, for what you are planning to offer, would you (honestly) buy your product over others, from someone like yourself? Remember, your little statement about "not competing with new cars" is exactly the opposite of reality. In fact, you would be directly competing with new cars.