He has gotten into a fight, one leg is hurt and hes limping. But he also has liquid black stuff around his mouth, and his mouth is quivering like hes cold, but he shouldn't be cold. i have a feeling hes dying.
There IS something you can do for your old cat. Call your local SPCA or Humane Society they offer very low cost/possibly free vet care for pets whose owners are low on funds. Look up the numbers on your computer and do the right thing by your cat. He's obviously suffering and miserable.
I'm really really sorry but I think you are right, the black stuff is likely blood and the shivering means he's going into shock. I really hope I'm wrong, but if this was my kitty I'd sure be running to the nearest Vet ASAP. ...prayers