Thanks for posting Eli - there are a lot of considerations here and I hope you find our insights helpful.
In terms of the "cash" part of cash crops:
What do other farmers grow in your area? Do they sell these as bulk crops to a wholesaler or distributor, or do they sell smaller amounts in local markets? if you have no access to a bulk procurer, you may have to focus on smaller groups of crop type, and stagger harvest times, etc. to make sure you can meet local demand throughout the year.
Do you have (or will prepare) adequate storage and delivery of your crops in their needed timeframes before spoiling?
in terms of water:
for your own future crop security, plan on planting as if you did not have a borewell; find crops that can handle lower irrigation levels, maximize water retention in ground through swales, zai pits, etc and mulch to conserve irrigation when applied(if you do drip irrigation, put the lines under the mulch, not above).
If you do this, you can conserve your borewell throughput for other uses, and your farm is partially protected in the event your well runs dry or lowers its output (which is a very real concern)
If you plan on selling locally, look into what crops command high prices, high demand, or are not present in sufficient quantity. these would be better to sell than your staple goods that go for low price or are difficult to process.
on a personal note - if you grow things that you like to eat or use, you are protected partially from market fluctuations, because you can be more comfortable eating your own produce if no one is buying.
I hope this helps