Hi Catherine! If you would like to sell on OpenSky, you will need to subscribe to one of our plans which are listed on the following page of our site: https://www.opensky.com/merchant/join/plans. On the other hand, if you are simply looking to purchase something on OpenSky, there are no costs other than those associated with the item(s) you purchase, which will all be itemized during checkout. If you have any additional questions, please feel free to call our Customer Love team directly at (844)707-7779, between 9 AM and 6 PM ET, any day of the week, and we will be happy to assist you further. You can also send us an email from https://www.opensky.com/content/contact-us if you would prefer.