they charge $5 monthly unless you cancel. So it looks like you could join for one month for $5 and cancel before the end of the month. See Below
You may cancel your membership at any time by contacting customer service by phone, e-mail, or live help. In some cases, you may be required to call customer service. You must cancel your membership before it renews for the next month and return all borrowed bags to avoid a charge for the next month's monthly membership fee. Upon receipt of your cancellation request, we will terminate your account at the end of the then-current membership period, provided that you have returned all outstanding products and paid for any unreturned or damaged products. If you paid discounted monthly membership or other fees based upon your commitment to a membership of a particular length or other specific terms, in the event you cancel your membership early or fail to fulfill agreed upon terms, your credit card will be charged for the full, non-discounted fees and charges for the entire period you were a member. WE DO NOT OFFER REFUNDS OR CREDITS FOR ANY MONTHLY MEMBERSHIP PERIOD. You will be given 5 days from the date you request cancellation to return all outstanding borrowed products or satisfy any payments for any unreturned or damaged products. Failure to return such products will result in charges to your credit card for continued monthly membership and other charges until all borrowed products have been returned.