Do I need any special license? Can I just call a supplement company who doesn't have online Canadian store and ask them to be an authorized reseller of their product in Canada?
I hope I understood this right! You are in Canada and want to sell USA products but you don't know how and don't have licenses! Yes?...
1-Find a local Canadian supplier that have the appropriate licenses to sell, meaning that they can import from USA,
2-Call USA suppliers and tell them you want to buy in bulk and sell in Canada and need wholesale prices.
3- Find an importing/exporting company with appropriate licenses and ship your products
4- Cut a deal with a Canadian distribute on monthly sales commission OR per quantity sales price and collect your cash..
5- I didnt get the part with online store!! Than you need to set up your online store??
BUT, make sure to start with local chamber of commerce or similar government offices to get understanding on what you can import and export, licenses etc... before you do anything.
I think the fastest way to get some useful information would be to contact a US supplement company that already sells in Canada, to discuss how they are currently distributing in Canada.
Then armed with this information, you can then approach the new US supplement company that do not yet have a presence in Canada, to discuss wholesale prices and Min Order Quantities.
Obviously it goes without saying that you need a plan of who you are going to sell to, for example direct to customers, or business to business.