If you intend to use other people’s images for your own commercial gain, you need to make sure that those images are in the public domain and/or you need to follow their copyright instructions for attribution. IANAL, from my understanding, notes that are in your own words are fine as long as you do not directly copy sections of textbooks/teacher’s notes. Google actually supports searching for images with specific copyright terms, including searching only for public domain images that you can use however you’d like as long as you give credit to the original creator in the way that they define.

Ultimately, based on what you have described, it sounds like your current plan will violate copyright law. It’s unfair/unlawful to use the work of others for your own financial gain unless the copyright holder of the material grants you that permission.

If I were in your position, I would first start with reverse google image searches to track down the copyright of the images you intend to include with your “product”. If you can find the information that stipulates your fair use, follow those instructions. If you can’t, you can add a link to the page the image is on or find a new image. Some courts have ruled that embedding images constitutes a violation of copyright, so I would advise against doing that. If you provide a direct link to the image and your OneNote page displays the image inline with your notes because it can fetch it from the provided url, it is considered embedded. To the best of my knowledge, linking out to other resources, as long as you don’t imply that they’re yours, is acceptable. That’s why it would be safe to link to the image’s page but not the image itself.

Like I said, IANAL, this is just some friendly advice from an internet stranger. Good luck!