I have grown tomatoes in 5 gallon pails before and they did just fine. I got the 5 gallon pails from a local bakery. Many of their supplies come in 5 gallon pails, and they were just throwing them out. There are a lot of foods that come in 5 gallon containers. You may want to check with local bakeries, grocery stores, delis, etc.
Just Googling, I found this article: Stores that hand out 5 gallon buckets for free.
http://fivegallonideas.com/sto...
Currently, I am using tables made of cement blocks, 2 x 4's and this shelving which I thought was reasonably priced when I purchased it from Greenhouse Megastore. They are 48 x 24 and cost me about $20 each for a pack of 5.
https://www.greenhousemegastor...
They are lightweight, can hold a lot of weight when supported properly, easy to manage, clean up easily at the end of the season, and give you the flexibility to re-arrange your greenhouse layout if needed.
Here was my simple setup last year using these plastic tops (against the sides of the greenhouse). In the back of the greenhouse, you can see two 5 gallon buckets with tomatoes (most were in my other greenhouse). This picture was taken on June 21st. These plants eventually grew all the way to the ceiling and gave me a lot of tomatoes.
This is a pic of my other greenhouse taken on the same day. These tomato plants were also planted in 5 gallon buckets.
