When you are broke and your five family home lives off of one income, it is really hard to be able to live healthy.
Get back to basics, yep, that means grow your own food. Before you tell me that is ridiculous, guess what, I do it so I know it is not ridiculous. If there is a family of 5 and only 1 income, that means that 4 people do not work outside of the home.
Now I understand that 3 of those 4 who don't work are children, BUT, it was not that long ago that children were expected to work the fields on a farm in addition to going to school. I am not saying you live on a farm, neither do I, I grow my veggies in pots from seed. Takes a lot of work, but it is cheap and I eat good and healthy.
Children can water/fertilize plants, hoe, weed, etc. It is good for them to get off of the couch and out in the yard doing work. Read up on making a raised vegetable garden in your back yard. There are all kinds of techniques for maximizing space and all kinds of cheap ways to fertilize (composting, saving coffee grounds and egg shells, etc) and organic pest control (diluted dishwashing soap) but it takes workers and with a family of 5 and only 1 income, you have workers available.
People can grow their own food, I know, I do it in containers. I live in attached housing so if I can do it, so can you!
Remember how your grandmother used to can veggies in the summer for the winter? I do, and I do it! That is a great way to have inexpensive, good food to eat in the winter when the veggies are out of season. Learn to can. It is not a ridiculous idea. I know, I do it. The other 4 family members in your household who do not work outside the home can do it. Children can help, I know, when I was a kid, I had to help my grandmother can veggies in the summer. I went to the U-pick farms and picked vegetables with her in the summer. Your kids can do it, too.