Tractor Supply has heavy-duty 5 gallon buckets for $3.99, and they are food-grade.
Plus, they are white so they keep your roots cooler than the black nursery pots.
I have dozens of them, drilled 1/2" holes around the perimeter, about 1/2" above the bottoms, so they drain very well.
Here's a link:
http://www.tractorsupply.com/tsc/pro...e?cm_vc=-10005
Home Depot sells white ones in the paint section, but they cost more.
I saw the "Big Orange" Home Depot buckets selling there for under $3. a piece.
Any of these utility buckets should last you indefinitely.
My white Tractor Supply ones are on their 3rd season in full sun, and look like new.