Desalination, typically reverse osmosis now, used to be a condenser plant, is still very expensive in terms of dollars per gallon.

As usual conservation is far more cost efficient than manufacturing your own fresh water. Flushing toilets, washing the manure, accounts for roughly 40% of the domestic fresh water used. Car washing and golf courses use a good percentage. Much of the fresh water use not actually used. As a result of the neglect of infrastructure many cities waste almost half of the water through leaking supply pipes. Many of which were installed in the 50s and have just been patched enough to maintain pressure.

Like it or not the majority correction/ cure is through community/ government action and long term.

In terms of what an individual person/ homeowner can do would be limited to private supplies - surface water, rain collection or wells if legal - water storage, conservation of what you may store, and what little reuse can be made of 'Gray' water.

Note that gray water, typically shower and sink water, cannot be stored long as it still contains nutrients that turn it brown and corrosive in a very short time. Essentially the only practical use is to water lawns or landscaping. Even use in a toilet is difficult because it can damage and/or clog flush valves and switching between gray and fresh water can be very problematic.

Storing water is likely to be practical mostly in terms of reserves for use if utilities go down. The numbers of gallons needed long term is so high that complete independence would require a large investment in cisterns/storage and radical reductions in use. Storing enough to get by on minimal use levels is only practical for a few days if you don't wish to invest in large tanks and cisterns.