Not really sure if it is a nursery you want to start, but Venero gardens near the MN Arboretum is a great place. They are looking for a buyer as they want to begin a new chapter in their life, but I'm sure that Jay and Dory would be happy to talk to you about their experiences, whatever your intentions.
http://www.venerogardens.com/ They are good people. And if you're willing to go another 8 miles west, you can come visit me and see my gardens.
I might also point out that there are few work schedules like that of a teacher's that favor time off over the summer when the bulk of gardening is executed. As a hobby gardener it's an enviable position. In most of the horticultural trades, your time is most precious during the growing season, and you may find yourself longing for your past freedom with summertime opportunities. On the other hand, if you like what you do, it's not work anyway!
Good luck with all your decisions!
