Without a well for ten years had forced me to get creative. I originally used a 1200 hundred gallon tank in the ground that was already here and put in by previous owner. It is about 80 ft above my house so I could attach some pipe and valves(lots of valves!) and rely on gravity feed for basic cold water. My learning curve was in one bad winter I had a cracked metal valve because I put water line in only about 12-14 inches deep. After repairing valve with an amazing fiberglass foaming product at HD- I better insulated the box the valve was in.
In 2018 I added my first hot water heater in a set up I call the cowboy shower. Using a 1.5 GPM Envirotemp heater that comes with most of what you need including the shower head handle, I began to finally take mini showers at home. But 1200 gallons wasn't much and the gravity is barely enough to make hot water more even. I also find it a bit cold to shower outside in the winter, though I do do it.
I fill my tank from a neighbor who lives above me since there is no buildings nearby the tank to use a gutter fill method. For a small fee my neighbor attaches a very long hose to my tank to slowly fill it about once a year or less(I use very little water with one person and a waterless tiolet).
Though I have since added many 55 gallon tanks under the eves of my house for garden watering, I just acquired a used 800 gallon tank from a neighbor.
After camoeing the exterior so I don't have to look at brilliant blue blob on the side of my studio, I began to retrofit the tank. It had sat in teh sun and though I paid only 200 for it I think it was too much. Every orifice, the lower feed, upper overflow, and the two that lead to a plastic see thru pipe monitoring the levels was busted. The small nylon fittings were easily broken out and I found similar nipples at Ace hardware and used epoxy to insert. The bigger fittings were unusual and I used a hodge podge of plumbing fitting to place with epoxy. Unfortunately I used a epoxy putty to attach a valve below since I could not find the size locally to junction the used valve to my piping......wont do that again. The tank filled in a month and then drained after the stiff epoxy putty failed.
I want to mention that there is no laws in Washington state that prohibit you from storing a couple thousand gallons of water or so. In some states there might be. But around here folks like to gossip about some imaginary restriction on storing water. For residential users in our rainy washington state this is simple not true.