Yes, eventually you’ll need a product to sell in order to make sales from your DM automations. (You make sales when your automation sends the link to the checkout page when someone asks for it).
That said, many of our students start by using DM automations to build their email list, offer free value to prioritize their content in the algorithm + boost engagement, and get people on waiting lists for their future products. (This is exactly what I did when I started).
You don't have to sell your own product, but eventually you’ll need a product in order to make sales.