how to list products from wholesale sites and add to the new site

I am completely new to e-commerce but what i want to do is pick all the products from specific wholesale product site and add 25-30% commission on each product and sell it on my site.

Questions

1: how do I get the list of all the products from the site? 2: how do I add commission margin to the products 3: I have not started a site if I start how do I upload all the products to ly site