Please help, respiratory infection

Long story short, a cat showed up at my place about 5 months ago and hasn't left. I called the number on his tag and the owner refuses to pick up or help his cat. He says he already has 16 cats I think this guy's getting neglected. He's constantly wheezing and has an eye infection. I live paycheck to paycheck so I can't afford another big vet bill. Is there an over the counter product I could try or a home remedy for his respiratory infection? I have antibiotic eye drops left over from my cat that I could use for his eye. Someone please help. This poor guy is suffering and I'm struggling to find help.

Hello and I'm sorry for this poor cat.  I'm also sorry about the situation; that there are so many people looking to do a 'right thing' and it is one of the hardest truths of our profession that resources are almost always, to a greater or lesser extend, limited.  However, as a vet my job is always to advocate for the patient's wealfare and this does not sound to be the sort of problem that's going to pick up if I say 'yeah, just give this (common household treatment) twice a day.'   Antibiotics have to be prescribed specifically for a problem - indeed it could be illegal to use soneone else's on this patient, as well as generally bad for every human who is prone to infections across the world (antibiotic resistance). Relativy few eye 'infections' are actually bacterial.  Wheezing is uncomfortable and a sign of some underlying disease.  It sounds as though this  patient could be beginning to struggle and at some point, without proper care, will deteriorate.  There is also the concern that if they have - for example, cat flu - your cats are being exposed to it.   Therefore my recommendation would be to take this cat to the vets as a stray and ask them to take care of it.   Vets will often aim to treat and rehome a stray if such a thing can be done and faing that, they can act to end suffering.

They could also scan your can for a microchip because it could be that they are owned and that there is someone who would be delighted to hear of their old friend again.