I just got contacted by a publishing studio that they wanted "non-exclusive reproduction rights" for one painting I made that they said could illustrate one of their concepts. It sounds real fun, but I am wondering a bit what "non-exclusive reproduction rights" actually mean, and what could I demand from agreeing on this? Getting credit for it seems fair, but what money or so? And if so, what would be reasonable as an amount to ask for? I am not familiar with being contacted by people who would like to use my art, first time kind of hehe.