Oddly enough, since I know nothing of the trade, I would go into farming, I mean I would buy large farms, small fields around and I would grow all sorts of things, I would sell them like that, but I would also have products from what I grew, such as jams, cakes, olive oil, etc, etc... I would go back to the basics, basically... I think people are too far away now from the land, everyone works in services, new technologies, etc and we are forgetting what is really important. I've often talked about this with my husband... unfortunatelly no money to accomplish this dream...
I would start an animal sanctuary for large animals. It would take a lot of money because I would want vets who specialized in those animals of course, as well as proper habitats. I would take any abused or homeless animal who needed a home and try to make their lives comfortable and safe. Lots of land and lots of help!
I actually would like to start a business or maybe a foundation that promotes study abroad. I think the world should require that every college-aged student live in a country for a year. It would have to be a country where the people speak a different language than the student-traveler.
I wrote a hub on study abroad and most folks feel that if they had the money they would study abroad. Hence there is a need for scholarships to promote study abroad.
In general, I think this would bring about world peace. People would learn about each other and understand each other. There would be no reason to fight or have war.