Currently, there is no way to make an add-on required. Therefore, anything required to book your space should be priced into your base rate and detailed in the Rules section of your listing.
If an additional service or fee is required depending on the number of guests or the time/day of an event, use the attendee and calendar pricing features to adjust your base rate accordingly.
Remember, add-ons are intended to allow you flexibility to sell premium amenity upgrades. They are not meant to be an itemized upcharging for basic amenities, like restrooms. Learn more about what you should and shouldn’t charge for here.
More details on creating, editing, and deleting add-ons from your inventory page can be found here.