What crops grow well with little water in dry climates?

Aloe, an ingredient in lotions, likes that climate.

You can also grow a lot of prickly pears, a cactus fruit.

Yucca should grow well, millet, maybe grain sorghum. You are not giving much information to work from.

corn

I live in South Australia - don't think you'll find anywhere drier!!  Olives cope with the dry and heat very well.  You might also like to try almonds.  There are a few old loquat trees in my semi-rural neighbourhood that seem to survive with a little supplemental water too.

Obviously desert plants and dry area plants, and enough so to give some choices, but they all are extremely slow growers and even they need occasional bursts of rain. Poor areas now that will slide into desertification with any environmental stress will be non productive in the extreme with no irrigation. For slower growing desert crops you need a head start and they need to be planted with the thought that more acres will be needed per person. Look to future trends in climate for a given area in question. Global warming is interpreted more as extreme conditions and weather, including increases and decreases to those extremes, with respect to temperature, storminess, and faster fluctuations and events. It is not necessarily a world heat wave as some envision.

Cactus

quinoa and amaranth
are low water grain like plants.

they are fun to grow and can
feed some one very well, and
I know this because I eat them all the time, and
occasionally grow them.

update:
it is worth trying to grow them, because unlike some of the suggestions that you got before mine, you can actually live on quinoa and amaranth

Agave
Then at least  you can distill it and have something to drink while you wait in vane for  global warming to make your crops valuable

Dates....as in palm trees

Look first at what is already growing there.
This will tell you what is really best suited to the soils and climates that you are looking at.
Everything has a use and its place in the ecosystem of the area it grows in. If you want to be as cost effective as you can, then find a use for what is already able to grow well without your intervention.
Be aware that harvesting too heavily may open up other issues about succession plants that can get a start and retard the growth of what was the mature phase of the landscape.
Be very careful about bringing in new crops, look what happened in the past with invasive species!