This unfortunately is a common business model that Amazon uses. If your products sell well and do good in the market, Amazon will steal your idea and compete directly with you. So many stories of this happening.
Amazon is evil. Never trust a business owned by a billionaire with defense contracts that works directly with the government. Aside from bezoar, ahem ahem, I’m looking at you Free-Lon Sus (Elon).
A great opportunity for you? More like he’s taking advantage of a young naive person for an opportunity for him. Why doesn’t he partner with someone experienced who has a track record of success? Because those ppl wouldn’t entertain that idea. Now ask yourself why. You don’t want to fuck yourself over like that.