Susitna-flower asked: ...where to buy barrels that would be "food grade" plastic?
(Guessing from your name, you're from/in Alaska - my wife is from the Mat-Su Valley, too!)
New barrels are widely available online. These can cost $50 to $100, depending on the vendor and their shipping costs/policies.
The best source, however, of the barrels is usually finding them used. Checking local food processors/factories and Craig s List are the best sources. Many places that use the things that come in the barrels don't reuse them and sell them for very cheap. We bought ours from a medical supply factory for $20 per barrel. They contained glycerin in them, and a good washing/drying purged the barrel of any remaining contaminants.
One last suggestion, if you are planning on storing the water horizontally, don't get "open top" barrels, as those will likely end up leaking.