The UC Davis ARE center does economic research on agriculture, and publishes cost and return studies on important crops in the state, including almonds, pistachios, walnuts, figs, and other tree crops. These studies can be helpful for developing a business plan.
You can learn more about the center here: https://are.ucdavis.edu/
And cost and return studies can be found here: https://coststudies.ucdavis.edu/en/