Here in Georgia the Dept. of Agriculture has a free publication that is all classified adds that have to do with farms, farming, live stock,… they are a great source for pick-your-own places and every now and again there is an add from a farmer selling half a cow.
So you might want to check with the Dept. of Agriculture in your state. I have thought about doing it, too, but we do not own a deep freeze and I am worried that the meat will spoil in the regular freezer, plus I would not have room for anything else. I also called the farmer once, wondering about going in with some neighbors, but he said that if more than 2 people want to “share” half a cow you run into problems with the different cuts and dividing it up fairly.