How can I get a vendor of phones to sell?

Like you see how all those peoples on ebay or these sell online type of websites that be selling all of those phones like iPhones, samsungs, lgs, zte, etc anything that's a phone. How do they all be getting all of those phones to sell and make a living? Like what's the trick? Because I know they can't just be spending thousands and thousands of dollars to get all those supplies of phones to make a living because it's like what's the point your spending the money on the product on that you just made the money with? So what's the trick? Because I want to run my own business online and sell phones and make a living? But how do i get started? Please someone help! Any advice thank you.

You need to come up w/a different idea or product to sell… As you have already found out, there way too many companies trying to sell phones ( and most of the sell very little due to the competition )