The curse of knowledge. You may know things that you think other people know because it's common sense to you, but many people may not know the things you know, especially in your field.

Make youtube/dtube videos about your field and general knowledge, and earn money through the youtube ads + look up relevant affiliate offers to your field (on sites like clickbank.com) and put those links below your videos + amazon ebooks related to your field which you can put under your videos and earn a commission when someone buys that ebook.