Emergency food can be fairly cheap

For years Wal-Mart has been selling a bucket of emergency food - enough for four people for two days - which costs $20. Not many buyers though, as every time I have seen them on the shelf it was fully stocked. Packaged to last 25 years in storage.

Besides that there are lots of possibilities. Grits are cheap and nutritionally complete if they have been fortified with niacin. They will certainly keep long enough for several months - or years - of quarantine.

Make sure to get some butter and salt as well, and bacon and cheese if you can afford it, to go with the grits.

Plus of course canned goods should keep for a while, and they're probably cheaper than what you usually eat, if what you usually eat isn't canned goods.

Don't worry too much about water. I expect the water supply will keep functioning. This isn't a hurricane or a drought.