How can a 12 year old can sell stuff?

A 12-year-old can sell items by starting a small business, such as a lemonade stand or a craft booth at local fairs. They can also sell unwanted toys or clothes online with the help of a parent, using platforms like eBay or Facebook Marketplace. Additionally, they can offer services like pet sitting or lawn mowing in their neighborhood. It's important for them to check local laws and regulations regarding selling goods and services.