I work at a pet shop and sometimes we get people who don't want to continue with the hobby of keeping fish and don't know how to use Craigslist or Kijiji, so they come to us with their stuff. This 5 gallon tank came to me with all the accessories inside -- castles, plants, heater, filter, thermometer, and driftwood. All I did was add in the gravel and the betta! Although I need to get a new filter for it, I bought new lightbulbs for the tank, water conditioner, food and treats, and my betta has been happy with it.
He's even blown himself quite the bubble nest!