What is wrong with this cat I found?

I found a very injured emaciated cat outside my house. It was having trouble walking so I brought it in to try to nurse it back to health. It is so skinny you can feel every rib and it feels like maybe bones are broken. It wouldn't eat cat food and seems to have an upper respiratory infection. I gave it chicken today and it scarfed down a thigh and half a breast and it's stomach swelled up on one side and is having more trouble getting around.I don't have the money to go to the vet so what should I do and what could be wrong?