The CFIA is explicit about the boundary: you do not need a Safe Food for Canadians licence to trade food within your province, or to prepare food that will be sold or consumed in your province. That single sentence resolves most of the confusion a new food business has about federal licensing. A shared-kitchen tenant cooking for sale inside one province is regulated provincially or regionally, not federally.
What triggers the licence is crossing a border, and the trigger attaches to a step rather than to a size of business. The CFIA states you need one if you are the last food business to manufacture, process, treat or preserve a food for export or interprovincial trade. There is a matching rule for pure middlemen: a business whose sole activity is interprovincial trade of food does not itself need a licence, but remains responsible for ensuring the food was handled by a licence holder.
Two qualifications are worth knowing. Provincial rules may still require a federal licence for certain commodity categories — dairy, eggs and fish — even for activity inside one province. And a federal licence never replaces the permit the premises needs where you cook; the two sit on top of each other.
If you rent space and plan to ship out of province, settle early who performs the last processing step, because that answer decides who is licensed. Confirm your own case with the CFIA; the licensing and permits guides cover the rest of the paperwork.