Good points Meta,
I would differ on the "green technology" subject. I live in an area with overflowing landfills and industries that are dirty and outdated. But windmills have started appearing around here, lots of them. Windmills require careful maintainance by well-trained technicians and construction crews. I see such new technology as initially expensive, but necessary, and very profitable as products and processes are discovered. As with electric cars, they are yet to be successful and will create many new jobs for enterprising people in the future. I won't cry at any loss for big oil and Saudi Arabia.
And if you really feel nostalgic about jobs shovelling coal, try it for a day. My grandfather was dirt poor as a depression-era boy. He and his father would look daily for work shovelling coal. He considered it as suitable work for convicted criminals. He celebrated mechanization in industry and agriculture.
As for investments, I agree that a personal small business can be very good, if done right. Additionally, I think the best investment is oneself. Invest in your health. If you don't have your health, you can't work. The future of healthcare is uncertain. So address everything now for the best health you can reasonably have. Also, invest in a good education. Not a BA in Underwater Basketweaving either. An education toward something that can help you find work that you'll enjoy for a long time. Learn things that will help you be self-sufficient and self-supporting. Along with that, invest in your children's and any other relatives education. Invest in friendships, since connections and networking are invaluable for finding work and assistance in any future time of need.