Can we evict someone W/O giving a 30 day notice?

From what I understand, if there is not a rental agreement then he is a "guest" in your house and you absolutely can kick him out without the notice. If nothing is written down, and there were no witnesses besides you and your roommates to the verbal agreement- you can even call him an "intruder" and have him forcefully removed if need be. (At least that's how it is up here in Idaho)