Rent a Kubota. Dig a 10'' square hole. Reinforce the sides. Add a roof. You are now the proud owner of a root cellar.
If you have an accessible subfloor in your house that also stays decently cool but it's not a great alternative.
Propane fridges are a good option if you can afford a $4000 fridge and full 500 gallon tank. (You can't lol)
Do not put canned goods in your attic. The temps in the average attic make the food degrade, separate, spoil, and get really nasty.
Dried foods like beans, peas, rice, legumes are a better option. (plus most bought grains aren't heat treated meaning you can just replant them in the spring)
Store water in those big food safe aluminum reinforced jugs. (IBC tanks, these ones)
OUT OF THE SUNLIGHT or any light if possible. I've known people who spray the containers black to keep light out. algae is a big problem with water storage.
UV makes these degrade and halves the life of the plastic.
Add about 8 tablespoons of bleach to 300 gallons to make it potable.
Fully cycle and wash about once a month if you don't use all the water.
Freezing is a major issue if you don't store them in a dark side room in your house or underground. If these freeze the whole thing cracks and you're out about 300 gallons of storage capacity.
You can get a harbor freight trailer kit for about $300 and tow strap one of these on the back. Fill from a well or if you need gray water you can source from a lake or something with a 12v pump. or a generator pump if you don't feel like waiting for an hour.
Keep the grey water and potable water tanks separate and labeled.
One of these tanks run about $100~$300 used, only buy used if they have been used for corn syrup or other food products.
Lots of these are used for pesticides. Do not ever buy them.
Chemicals stay in the pores of the plastic forever, you cannot wash the chemicals out.
Always ask the seller what was stored in them or if you can afford it buy them new.
Source: Grew up off-grid and we didn't have a well until about 3 years ago, almost never ran out of water, just filled the reservoirs once a week with a trailer with two of these. Always had water for showers, the farm, cooking, etc. A neighbor would trade well access for some gas for the generator. We had about 7 of these in a side room in the cabin, half for grey water, half for potable water. We also had separate lines for P and GW. If you can get a well. It makes life 10x easier.