Going to fetch an older iMac in a few hours: It's old enough to have 10.6 (Snow leopard), but new enough to have a pretty flat display. I need to update it to at least 10.11 (Maverick). I was asked to reformat it as well.
Anything I should know? Will an OS-update cost money? Do I just turn it on, connect it to the internet, and Apple does the rest?