Thub is right. If you don't own the copyright for your material, I'd be careful about monetizing them. It's not likely that you'll be banned if YT catches it but you won't be able to monetize the video and it could be removed. <---I've never had this happen myself (was just told 'No' and the video stayed active).
But, there's nothing to it.
Keep in mind, though, right now there is an EXTREME delay in YT approving videos for monetization. I have some that have been waiting on approval for well over a month. It's brutal. So, don't expect this to be a big revenue stream right now.