For some situations, you may want to offer a free product or have a promo code associated with a free product.
ClickFunnels does not allow for a product to be priced less than $1 USD.
But you can use this workaround to create a "free" product:
Do keep in mind this is a workaround directly from ClickFunnels, and this help doc belongs to ClickFunnels. If you have further questions on setting this up, please feel free to reach out to their support for further info.