Step 2: Where To Find A Barrel?
1. Craigslist: This is often the easiest way to find a barrel. Where I live, people commonly sell them for $10. I would not pay more than $15. If you just search for "barrel" you should find something. Check what was stored in them before you buy them. I have found some with liquid smoke in them that have been a real pain to deal with and they never really stop smelling. They should also not have had any toxic chemicals stored in them that could harm your plants. I would encourage you to ask if the seller is willing to trade anything for an empty barrel. Many people on Craigslist are purveyors of multiple goods or are familiar with trading for goods. It can be worth the effort to ask. You may get a free barrel or two for trading some junk that you don't need.
2. Local Food Distributors/Bottlers: This could be your best bet and was my method of choice. You will have to do some research and call around your city to find out if any food distributors use 55 gallon drums and if they would be able to give them to you for free or sell them at a low cost. Common uses for the drums include soda syrups, juice, soy sauce (my most common variety), grain alcohol, hops for beer, marinades, liquid smoke, etc. I googled bottling companies in my area and made many phone calls. If you are polite and present clear questions to the people who answer the phone, you may get exactly what you need. I was able to arrange to pick them up locally for free if I did not disturb the area around the facility. This arrangement worked great for me for a long time, but each scenario is different. I have head that some Pepsi/Coke bottling plants give them away, while others do not. If you are looking to make multiple rain barrels, this could be your regular supplier. Don't give up after one or two calls, I think I made about one hundred calls before setting up my particular arrangement. Seek and ye shall find.
3. Pickles/Olives: I have met multiple rain barrel makers who get their barrels exclusively from olive or pickle distributors. . Go to your local grocery store and see if any of the pickles or olives are distributed locally and make a few phone calls to see if they have barrels. The barrels that contain olives and pickles are commonly larger and have a large screw lid, but they can be easily used to make the same type of rain barrels that I have designed.
4. Car wash: Many local car wash places get their soaps in 55 gallon barrels and they will sometimes give them away. I have found this approach to be more work than its worth because you will have to rinse the barrels many times to get the soap out, which can defeat the purpose of rain water harvesting. In reality, you will most likely have to rinse any barrel you find, so I guess my point is moot. This is often a viable option. I would also steer clear of the white or clear barrels common at car washes because they let sunlight in and can encourage algae growth.
5. Vineyard: For a fancier rain barrel, you can also try calling local vineyards to find out of they have any used oak barrels for sale. With a little more effort and more upfront cost, you can have a great looking rain barrel at a fraction of the cost of a store bought oak barrel. I bought mine for $80 each, which I found to be a common price. With a little shellac the barrels can last forever.