A modder known only as Fluffyquack (I like to think that's his real name) has added offlineto the game's first episode.
For now the mod only works with gamepads, rather than mouse and keyboard, and you can't use it in Raid mode. Capcom's stated that they're already working on adding online co-op support to Raid mode, and Fluffyquack hopes to convert it over to offline when that happens.
To get the mod working you'll need to download Fluffy Manager 5000, which also mods basically every other Resident Evil game available on Steam.
Capcomfor not making clear that offline coop was cut from the PC version of Revelations 2, and claims that it is “currently looking into the matter and potential solutions.”