Most people wouldn't grow or need that much for sure. Most also, unless they've had a lot of experience, will not get that kind of weight from a few plants. It is amazing though how much more you go through when making medibles, caps and the like. I use 10x more in medibles than I'd ever smoke in a year.
As far as them worrying about you selling it, idk how much of a factor that will be once it's legal for recreational. Think about it, it will no longer be hidden in the shadows, you won't have to know "a guy", available anytime, anywhere, likely more or less unlimited.
Once we get through the initial "newness" stage of legal weed, only hard core hobbyists, specialists, and large scale ops will grow it, and the "taboo" factor will be gone, even for CONservatives