Depends on who is signing. When I went to Phx Comic Con all the artists had stuff at the table you could buy and then have signed. You could also bring your own stuff in, but they usually limit it to 1 or 2 sigs per person. Other people who aren't comic book artists usually charge for sigs or pics. We paid $5 for a pic with the kid from the walking dead. If you have something specific you want signed from a specific person then bring it, otherwise just bring a signature notebook, or buy something at the Con. The majority of the Con is a big shopping mall / artist showcase so bring lots of money to buy goodies regardless.
