UPDATE -- Capcom USA PR Manager Briant Keltner has clarified to Co-Optimus that the first Raid Mode stage is unlocked after finishing level 3. So it's still not initially available, but at least you won't have to get through all 10 hours of the campaign for it.
ORIGINAL STORY -- Were you planning on playing Resident Evil: Revelations' co-op mode out of the box? Unfortunately, "Raid Mode" is locked until you finish the main campaign, and that feat alone will take around 10 hours.
Andriasang reports that Raid Mode is unlocked after finishing the game, along with characters like Jessica and Obrian, who are unavailable to play in the main campaign.
Because Raid Mode is one of the explanations for the game's unusually high $50 price tag, it's strange to lock the content away. In addition, the game will also support the Circle Pad Pro, meaning that users wanting the full and supposedly ideal set-up will have to pay for it too. Killing zombies is expensive.