For the most part, yes. However, some offer periodic free listings to entice new users. Sales commission fees are calculated as a percentage of the item's final sale price at the close of the auction. First, you must register with an online auction site.
Most sites provide tutorials or information on how to list items for sale.
You'll need to include a written description of the item, a sales policy, and, if possible, a photograph. Explain what forms of payment you accept, if you wait for checks to clear before shipping, when you expect payment, how much you charge for shipping and handling, if you require insurance on shipment, if you accept escrow, and if you offer money-back guarantees or refunds. It certainly helps. Having a photograph is a big plus. If you have multiples of an item, you can sell your merchandise on more than one site.