I actually bought a 55g off of CL today for $45. It was really dirty, but I spent 30 minutes with some hot water really cleaning it up. Going to finish it up with some vinegar later in the weekend.
In any case I don't think this will be used for this project as it didn't come with a stand and it will likely take me some time to get a proper stand for it separate. However if nothing comes along in a week or two I might consider moving my (very heavy and sturdy) dresser over for the tank and using it, will have to see.