Sounds like a plan...and an exciting one at that!
Since you will be growing seedlings, I would recommend twinwall clear polycarbonate or clear greenhouse film. Neither is 100% clear, but either will diffuse the light much better which is good for seedlings, and they protect seedlings better from burning or scorching than a clear glass greenhouse.
Sounds like you most likely will need room to grow your greenhouse as your business grows, so I advise looking at greenhouses that can easily be added onto as needed.
Growing winter crops without any source of heat is a real challenge in your climate. I am working on ways to naturally heat my greenhouse. There are also ways to add seasonal insulation without changing the structure of a greenhouse. Cold frames and row coverings are a good idea, and there are more.
I am excited for you and your project(s)!
