More photos are taken every hour in the modern world than were taken in the entirety of the 19th century. Let that statistic sink in for a moment. We take more and more photos every day, and most of them just sit on social media, or our computers, making us no money. There is a massive demand out there for stock images. You'll see a hundred of them on the internet today. Those pictures have to come from somewhere.
Online agencies are happy to buy photos from you for resale as stock images. Take quality, generic images of buildings, scenery, yourself, your office space, your car - anything you like! People will use them and re-use them for various purposes on the internet, and every time they do, you'll get a royalty payment. The more photos you'll take, the more you'll earn. Plus, you get a new hobby out of it.