I'm about to sell a range of images to a client and he asks me for a document to "sign off attribution". What does this mean and where can I find sample contracts?
It sounds like he wants you to sell him some type of agreement to either reprint, or use the images as you agree to. An example of attribution from the creative commons license:
Under the Creative Commons Attribution license, commonly abbreviated as CC-BY, you are free:
to Share — to copy, distribute and transmit the work to Remix — to adapt the work Under the following conditions:
Attribution — You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work).
If you are looking for examples I would take a look at this previous question already here: