Actually, harmful acid rain is quite a rare occurrence. I would be more surprised if acid rain actually happened where I live.
Anyway, you can make it free if you so choose. While yes, it would be hard, but food and water can be free. Wild fruits and herbs are completely free (and come are easily transplanted and/or hardy), as you could possibly find them in your own backyard. There is also wild game, such as deer or birds, and possibly fishing. Water can be collected in rain dishes or tapped directly from a pure water source (like my cabin in Pennsylvania. It's tapped directly into the mountain). It's not impossible, but it would be extremely hard to live this way. Also, not all areas are as plentiful as where I live, so difficulty is variable. But, like I said, it can be free.
As for our human market for food, no, it shouldn't be free. Food is one of the biggest markets in any country, and making it free could potentially lead to a depression. Possibly even an economic collapse (a long stretch, but it could happen).