This is a hypothetical question.
Suppose I were to open a photography gallery in a shopping mall. What legal issues (if any) might I face if I were to display and sell images of performers without their permission?
Specifically my question is relating to concert photography, however I am somewhat interested in learning about other scenarios aswell.
And, assuming there are issues with the above scenario, what sort of permissions does one need in order to avoid problems, and how would one go about obtaining such permissions?