https://www.costco.co.nz/terms-and-conditions
Membership
- Membership is available to all qualifying* individuals 18 years of age and over.
- Costco reserves the right to refuse membership to any applicant and membership is revocable on notice to the member without cause. Your membership fee will be returned in full if your membership is revoked.
- Membership is subject to any and all rules adopted by Costco including our privacy policies and practices, and they may be amended from time to time. Any changes to these Privileges and Conditions of Membership will be posted online and at the membership counter. If you are not happy with any of the changes we make, you may cancel your membership and receive a full refund in accordance with our returns policy.
It never actually delves into what "qualifying" entails.