You sir, are absolutely correct. He should go for whatever he wants to do. But you are comparing a Million dollar + venture to a Clay pot that plants grow out of, a rock and a small device that clicks on the lights. While they are worthy inventions, they are small, cheap to conceive (hell I got 500000000 pet rocks in my backyard) and are easily mass marketable.
He seems to be looking for something to do, not really invest in per se, but do. He wants to do something. But the scale he is wanting to do it on is huge. Hell, he hadn't even thought of insurance, EMT's and paving. Like most of us when planning something, we skip over the getting there and go straight to the money.
So, while I think it would be a great idea, it's a nigh unattainable one without a hefty investor with lots of capital.
Let's ask the grading guy. Put together an estimate on a lot the size of a Target, with parking, slideout zones for out of control cars, pavement and the incredible amount of barriers you are going to have to have to satisy the city. That is just one part of this venture. Because you won't get away with flags like DGTrials one day events, not being a permanant site.
I can tell you this, I think our Insurance costs were right around 1000-2000 (depending on who we used) for just one day at a Seda event. I think the lowest we got it down too was $500. For one day.
It's not as easy as it sounds. By far.