Try contacting local restaurants, beverage bottling factories or large shipping companies in your area to ask about free plastic barrels. You may also be able to find them on classified websites, such as Freecycle.org, but treat these listings with caution.
Some people use plastic barrels to store pesticides, detergents and other harmful chemicals. When you get free barrels from a private source, you may not know the history of that barrel, and it may contain dangerous residues. This is especially important if you plan to store food or water in your barrels.
Breweries and bakeries are other good local sources of plastic barrels. These sources use food-grade plastic, which is essential for safety if you plan to store food or water in the barrels. You may also be able to find barrels at local recycling companies. Some local governments offer free rain barrel kits, which include plastic barrels, so check with your city or county government.
If you cannot find free plastic barrels in your area, try searching for a company that sells them for a lower cost than your local hardware store. Some specialty container companies sell plastic barrels for under $10 each. However, some of these companies require you to buy a minimum number of barrels, especially if you cannot pick them up yourself.