I've only sold one item myself.
Someone contacted me wanting to use a picture of mine for a logo.
It was a small mom and pop business so I was nice. I still got a good amt I think for it: $130 just to make them a quick logo out of the image.
I wrote up a simple contract that said they could use it for their business only but that I still held rights to the original image to use it any way I wished as the owner. Took a bit of looking around to get the right wording too. First contract I'd ever written up on my art.
I had a disc with legal forms which helped me get some of the wording and I found some sites online with contracts too. I just combined a bit of everything to get it the way I needed.
Anyhow... that's my one freelance experience.
~L~