Lisa, don’t be afraid of keeping a tank.
I have a 50 gallon “sheep” sized stock tank from Mills Fleet Farm. I want to say it cost me about 60 bucks when I bought it. I screwed in a valve that they make specifically for these tanks into the hole in the bottom, and ran a hose into my floor drain in my basement. Draining is as easy as opening the valve and going outside to play with my kid for 6-8 minutes on the swingset. If we go too long on the swingset, no worries, as the bottom 2 inches of water in the tank don’t drain. Filling is as easy as turning on the faucet above the tank and letting it run for 4 minutes. I don’t do this unsupervised, as you can imagine the mess if I overflowed it.
I never used to have a filter at all, but now I have an aquarium filter. It’s not the most expensive one on the market, say about a $40 unit. The pump was 10 bucks and air stones $10. Tubing probably added another 10 bucks. So your total cost should be over $100 but probably well under $200 — most likely under $150.
Even keeping as many as 50 bullies in there, I can go at least 5 days without a water change. If I only have 2 dozen or so, I can go over a week easily. I add some of that water starter that the aquarium folks use. It costs about 4 bucks for a bottle and that bottle easily lasts a month worth of water changes.
You can also go with something more like a rubbermaid tote, but then you’re going to need a way to get the water out of it — bucket, sump pump, etc. Also, if you do the rubbermaid tote route, be sure to build a wooden frame around it, or those totes will tend to burst at a corner eventually due to the flexing because of the heavy water on the sides.
Here it is — nothing fancy by any means, but it gets the job done — the filter’s not on there but you get the idea. The valve is at the bottom front with the yellow handle. Before last season, I also decomissioned the file server you see behind there and moved that wash tub out, so that the tank could be moved back against that wall and out of the way providing better access to the furnace, etc.