Have a yard sale to sell things you no longer need. Choose a day or a couple of days to have your yard sale and advertise it in your local paper and online, such as on social media and classified websites. Then, on the day of the sale, arrange the items on tables, blankets, shelves, or in other ways in front of your home. You can arrange the items into groups by price, or price them individually.
Go hunting or foraging for food. You may need to invest in gear and permits, but if you already have these, this is an inexpensive way to get your own food. If you're ethically against the killing of animals, it's pretty easy to forage for food, depending on where you live. Just make sure to forage only for food whose origin and properties you are sure of. Getting sick or poisoned is never any fun.