How would I go about letting other people sell through my website, but they handle shipping and stuf

A friend of mine has a book and a large fanbase, mainly of people who also write books, specific genre of them. So I was wondering, with my friends support I could make a website, allowing these folks to sell their books through my website (using wpmudev plugins!) but im wondering if anyone could offer some advice about going through that, like what if the person writer does not ship the book, what part do I play in that? Also, if I would get a fee per sale, how would that work, like do I have to count on the person paying me what ever they owe or what, how would i deduct the money, assuming that the buy will be paying the person directly, or maybe I would have to accept all money first?

Any help is appreciated