Depends on how you wanna play it. If you mean just one play through on medium difficulty on co-op, maybe 8 to 10 hours i’m guessing. If you wanna get the achievements, play through the unlocked hardest difficulty after you beat it once, and get the best weapons, maybe 25 hours.
Haven’t touched the versus mode online, so I dunno anything about that. But if you wanna just play through the campaign once co-op, rent it. You can beat it in a week, couple hours a night.