The "Five Gallon Water Jug" is only $10. If you keep it in a dark place, it can't be beat for an economical solution. I've used some over ten years. Both indoors and in a storage shed where they freeze. Never had a problem.

I would also suggest two of these 7 gallon jugs with built in water filters. One as a backup of the other. Stick them in seperate locations. Perhaps two different closets. Aqua-tainer® 7-Gallon Water Container