Consider selling in lots. A lot is a collection of similar items that is sold in a group. For example, if you have a collection of books, magazines or similar pieces of jewelry, consider selling them all at once in a lot. You many not make as much money as you would have if you sold each item separately. However, the items will likely sell more quickly in a lot than they would individually.
Monetize a hobby. While some hobbies actually cost money, others can be transformed into a profitable business venture. Ultimately, it depends on what your hobby is and how talented you are. You could turn your love of photography, for example, into a part-time gig taking family portraits and wedding photos or selling prints on Etsy or at arts fairs.
Some of the best things in life are free and market researchers love to hand out new products in exchange for consumer feedback. If you like to try new products and have the opportunity to try them out for free, do some research and find the market research companies that offer products you desire to try. You can join campaigns and they will send the products or coupons to you to test them and provide feedback. You will generally have to fill out surveys and provide written reports based on your opinions. You will get to keep the products and they will sometimes even send you a monetary gift as an offer of thanks for doing the work.