Wow thanks for the responses!
Basically, I have one friend who's a vet and another friend who works in health care and can get me a good deal on diabetes supplies like insulin. I suspected Smokey was diabetic, and sure enough he was just officially 'diagnosed' by my vet friend when I was finally able to take him in. I'm feeding him fancy feast, so I guess that is o-k? Also, if i get a glucometer and test strips, what numbers am I looking for? There's no way it's the same for humans and cats, right?
This is his only health problem so far, before this he was very healthy.