Bulk and Prices

I've wanted to start feeding raw for a long time now. I have a young mixed male with some renal issues and know a whole food diet will help him immensely. He is already on a grain free food but I want to do better. I want to know where you would recommend I contact about getting meat at a decent price. We have meat markets in our area, what do I ask them? I've heard of meat processors, but where would they be located? I'm looking for the cheapest prices I can get:)
He should be around 40-50 pounds, he's been bordering on 37 for weeks without weight gain and he's pretty slim, thanks for the help!