My neighbor neglects his dog?

He's a nice guy, but he leaves his dog outback in a tiny area with lots of weeds, a little, puny igloo dog shelter, and two empty bowls. I don't want to report him because he's really nice, but the poor dog is unhealthy. The dog has a raw nose with sores, the guy said he has a growth on his stomach, he thinks it's cancer and he can't afford to pay for vet bills anymore, so he's just hoping the dog (his name is Cowboy) will just die naturally. I, on the other hand, disagree. My mom went in the back gate (she didn't think he was home because he stays in his house all day with the blinds shut, the guy never leaves) and she filled up his bowl with water and gave him some of my dog's food. The guy came out, and he was like : "Uh, hello?" He wasn't mad, just shocked, and he said we could take Cowboy out anytime we want. He's a 9 year old Lab. We already have a puppy, and we couldn't afford vet bills, especially since the dog would probably need many surgeries. He's still active, because I went over and he jumped on the fence and I fed him chicken and some of my dog's dog treats. I want to give him to the shelter to take care of him since I don't know if he has any contagious diseases, and I don't want him hurting my dog. Do you have any ideas of what else I could do? What could be causing his raw nose and growth on his belly? He's been out there for about 2 years, when I used to go out and wait for the bus (the bus stop backs up to the fence), he was out there.