What about the cost of watering it. Perhaps as an added contribution you can give them a few bottles of the final product. Consider growing tomatoes, peppers and cilantro and putting up some delicious salsa, as well as plain tomatoes, for a rainy day. Sprouting seeds cost pennies to purchase, yet yield big dividends in nutrition. Don't wait to learn how to grow this economical source of greens.
Sprouts are tasty additions to salads, sandwiches, soups, and stir-fries.
Plan a menu and stick to it. Store what you will eat. Don't just arbitrarily put together a food storage list. Systematically develop your storage, according to you and your family's food preferences. Sit down with family members and organize a plan.