The only motive I have for feeding corn is that I can aqquire much much cheaper. I now know that it is nt a good balanced diet for them but if all I had was corn to give them what would be some good things to give them to help balance out the diet. Like I said they have partial free range and get plenty of scraps so the crack corn would probably only be about 50% of their diet. Any ideas on particular scraps that are better than others or would be a good supplement to this diet? Keep in mind cost is a very very big factor.
Just do the best you can. They may not live as long, lay as many eggs or be as healthy as with complete nutrition, but just do the best you can. Main thing to balance out the nutrition of just corn is to get them protein, ideally some amount of animal protein. I pay $1.60/lb for fish meal (comes in a 50lbs sack), which is pretty darn cheap for animal protein. I feed about 20% of their protein intake as animal protein, the rest is plant-based. Or you can use soybeans...be sure to get feed grade soy (it has been heat treated to destroy toxins), I don't buy soy but I think it's fairly cheap. Soy isn't as good as any animal protein, but it's more complete in terms of amino acids (important) than other plant proteins. In fact, the basis of many chicken feeds is corn and soy. Since cost is a factor to you, you might try your local grocery stores to see if they might be willing to give you their produce they are no longer able to sell, for cheap or free. Perhaps food banks might also have something to contribute?
Also, free range them as much as you possibly can...they can forage for quite a bit of their own food if they have good land to do it on and have enough time to do it. Predator attacks is an increased risk, but that just tends to go with free ranging.
In terms of scraps, give what you have, ideally a variety. Nothing with too much salt or cheese, ideally.