***UPDATE***

Drove by the house where we've been feeding the cat this evening and the owners just happened to be outside. We pulled up, and with the coaxing of my husband, we both went and inquired about the cat. Supposedly he's 20 years old and healthy. They said he's very thin and they've had him to the vet, but all tests were OK...so that will be one less worry now.

I told them we rescued stray cats and noticed this one wandering around and wanted to make sure he had a home. They didn't seem too upset, but were almost apologetic about his appearance. Said their son brushes him, and lets him come in and out of the house. I still feel questionable since he does look so bad, but will assume they're telling it like it is. I'm glad my husband shoved me out the door to ask! haha