craftgrrl | Question about selling our works

If I use a pattern that I have purchased, or that is available for free (say for 3d beading little animals and such), can I sell what I make? Or do I have to create original patterns for this to be ok? I'm not entirely sure how this works. I did a bit of poking around Etsy and see someone selling beaded Disney characters...is that a legal thing? I guess I just don't understand how copyrights work in regards to making and selling our own items using someone else's characters or purchased patterns. I recently discovered I love love love making 3d beaded animals and would like to find something to make a bit of money on too.

Thankyou :)