How do I get permission from companies to sell their products?

I want to start a delivery service that brings convenience store-type items to customers. What are the main things I need to know to start this project?
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Contact companies with whom you want to do business with and negotiate to buy a supply of their products so you can resell -- having everything you need in place administratively and legally to be a reseller in your area.

For your delivery service, you can charge a flat fee or a per delivery charge -- whatever scenario makes the numbers work for your bottom-line profit and for your customers.