One of the cheapest ways to store larger amounts of water is by using water bags rather than drums. An even cheaper way - if you have the space - is several plastic garbage cans with lids. A thirty five gallon can at Home Depot is about 20 bucks in my neighborhood. Just remember to tip them over and replace the water every six months or so. Also advisable is a good filter like a Berkey to remove any odd tastes picked up from storing in the plastic cans.