A shelf full of gallon jugs of water, protected from light so no algae grows in them,, is a simple step almost anyone can take. A few cases of Ramen noodles won't cost much and will slip under your bed. A few extra flashlights and a large pack of batteries, some cans of beans, and you've made an excellent start on emergency preparedness for under $100.
What if the toilet won't flush? If you keep a couple extra boxes of trash bags you can open them to line your toilet for pooping. An industrial-strength debris bag can hold these poop-filled bags until the crisis is over.
Think about ways you depend on continuous electricity and devise alternative strategies.
Electric range? Have a camp stove and fuel and use it outdoors to avoid asphyxiation and fire risks.
Electric alarm clock? Have a windup alarm clock.
Burglar alarm? Get long duration battery backup.
Refrigerator? Keep a supply of non-perishable food.
On a well with electric pump? Keep 100 or more gallons of water in storage, plus a roll of poly film to deploy for rainwater catchment. If your well is shallow, consider investing in a manual pump for backup. Also consider an inexpensive gravity-feed water filter like this one: http://www.cheaperthandir... that screws into the bottom of a plastic bucket.