There’s more than $2.1 billion of art for sale at the New York auctions next month. Almost half of it, including an Andy Warhol painting belonging to billionaire Steven A. Cohen, already has a buyer before the first paddle goes up.

When the two-week sales start Nov. 4, $1 billion worth of paintings and sculptures are guaranteed to sell by Sotheby’s, Christie’s and Phillips at minimum prices regardless of what happens in the salesroom. The companies are lining up deep-pocketed backers for the guarantees or financing them with their own money -- a risky proposition because they can end up owning the works if there are no takers.