used aquariums

bought a used small tank from a kid to use as my fish "hotel" when I stay at my parents house more than a few days. It's filthy and I want to make sure that whatever disease finally killed his betta (never cleaned it... his dad told him if it had a filter it wasn't necessary. Ha!) Best way? The...

I am looking at some 4 and 6 foot tanks used, online. Some set ups seem reasonable, until I look at prices elsewhere that are cheaper. What are used tanks going for in your areas?