What sort of products are you talking about?
Depending on if any of the concerns listed below could apply to the products in question, it would be smart for you to get in writing and signed by your friend a statement saying that all rights to the remaining products are being turned over to you and that you are allowed to "do what you want" with them, prior to marketing them online or elsewhere.
Otherwise you could find your friend expecting all or some of the money you make in the sales - your friend disputing, in other words, what you say he said to you orally in regard to the products.
And this is assuming all sorts of things about the products from his company - one, that your friend held the right to sell the products to begin with and, two, that the products being sold are not illegal items (e.g., counterfeits, some licensed products) and, three, that the products comply with all safety regulations (e.g., that they were not recalled for dangerous defects) and, four, ... well, the list continues.
Very generally speaking, re-selling items that have been legally purchased or that are legally owned is allowed.