How to: Settings > Payments > Offers
Adding an upfront fee to your pricing
When creating an Offer, the second step will have you setting up pricing. Here, you can turn on the "Add an upfront registration fee" toggle to set a one-time upfront charge.
Currently, this is only possible for Tiered Membership Offers, as with Digital Products you can instead have your members pay in installments or as a one-time fee: