Food grade plastic buckets can be found for free or fairly cheap ($1-$2 each) by checking with Dunkin’ Donuts, grocery store bakeries and restaurants. Some throw them away and will be happy to sell them. The fillings and glaze coverings for donuts all come in buckets. Fast food restaurants get their pickle slices in buckets (the strong pickle flavor/odor will be hard if not impossible to remove from the bucket-watch what you store in these, it will absorb that pickle odor).
When you get used buckets (make sure you ask for lids!!!) you will need to clean them out, even if they are clean. Take a butter knife and pry out the rubber gasket in the lid. Wash everything and then make sure it’s totally dry before using. Watch the thin plastic buckets, often more square shape, but sometimes round. You can almost see through these. They will get brittle and shatter (after 10 years or so) if dropped and faster if the sunlight gets to them. I wouldn’t necessarily pass them up, just be aware that they have this weakness. Buckets without lids should not be passed up, they will be needed to haul water, compost, during a harvest and a million other uses.
Have a reason for wanting a lot of buckets so that you don’t stand out. If you can get buckets from multiple businesses, this will spread the operation out and provide better cover than buying everything from one business. After you buy a bunch, the businesses will either start charging or charge more. You will create a market. They need to make a living, too. Compare what they charge to buying new buckets and you will still be getting an incredible deal.
Buckets could be buried if needed and they will last a long time underground. Only the handle is metal. Remove that and a metal detector won’t find caches of food and other supplies.
Another option is food grade [plastic] barrels. These can be filled with bulk food like rice and grains. While harder to obtain, they can be valuable to store bulk foods. I would suggest that a person use large food grade plastic bags to store multiple bags of food within a barrel rather than a full 55 gallon barrel of grain. A full barrel will weigh around 500 lbs (depending on what you store). Multiple bags helps you to be able to remove a smaller quality without exposing the entire contents to moisture in the air when you pull some supplies, and it’s easier to handle. Barrels can also be buried as a cache and a metal detector won’t pick them up (unless you fill them with lead, brass or blued steel). If you have a few barrels, invest in a hand truck (around $50 at Sam’s Club, Tractor Supply, Home Depot, Lowe’s, etc) so you can move them around.
A warning on storing rice. We have stored food for 20+ years. I have found some plastic rice bags to have the ink printing get sticky after 10 years. Somehow it breaks down and is a mess. The rice inside is edible, but removing it without getting that ink on it is tough. Is the ink poisonous at this point? I don’t know. It takes a lot to wash it off your hands. Break it down into clear food grade plastic bags to avoid this. – Don in Ohio