1. You're not allowed to monetise copyrighted content or even mashups of copyrighted content (even if they would be fair-use legal). The invitation is automatic and may therefore be mistaken
2. Don't expect to see more than a few cents unless you have thousands of views per video. At first it will only be showing those pop-up ads not the pre-video full ads.
3. There are ways around the automatic copyright detection (like changing the audio/video slightly) but they will catch up if you don't keep changing, reuploading and changing account. It is not worth it unless you ARE doing something legal and have thousands of views.
The only people who make money out of Youtube are people who spend hours each day producing substantial, original content with tens of thousands of views per video.
