I don't have great answers but here is what I have done.
Grab a few cases of bottled water from Costco Walmart whatever. Throw them in the basement. Pretty cheap.
Take empty two liter pop bottles. Triple rinse them and fill them up with water, and throw them with the other water in the basement. Free, but you shouldn't drink soda pop.
We live within walking distance of a major river (1/2 mile). If things get rough, I can go get water there.
Water filtration
Big Berkey water filter. We use this normally to get the flourine and chlorine out of our city tap water. The Berkey could also filter the river water for us. They are a little spendy around $300 I think.
I also have several Sawyer mini water filters (backpacking type). They are small, portable, and inexpensive at about $20 each.
I also keep some bleach and pool shock for that option. Boiling us also an option.
Ideally, I would want a well with manual hand pump. Not there yet, as we still live in town.