ebay charge a 'listing' fee, there are also different charges if you want a bigger picture or more than one, different layout, gallery picture and on and on and on.

The fees are all here

also if you accept paypal then there is another charge if people pay with credit cards. normally have the PP charge enough to cover the post & packaging & charges.

I think you can use your paypal account to pay the ebay fees. here

hope that helps.
it was a bit confusing when i started selling a few things but once you get past all the setup stuff it easy enough.