Many people have made money online by cleaning out their houses and selling all their unwanted possessions.
It is basically like a garage sale that takes place online. You can do this easily on sites like Gumtree, or eBay by simply uploading a picture, writing a short description and uploading it.
After all, one man's trash is another man's treasure.
If you do not have any unwanted possessions that you would like to sell, then you can always try drop shopping. Drop shopping is the act of selling products for another company and they will take care of the shipping and other related costs and services. A great way to do this is by launching your own eCommerce store and uploading the for sale items online.