Hi there,
I am presuming that none of the cats will have been vaccinated, so they are more than likely to be suffering from cat flu which causes sneezing, congestion, runny noses and eyes. The also may have FIV or FELV both are diseases that can be picked up by each can if they have no been vaccinated.
To be honest they will all need veterinary attention and probably antibiotics and or eye drops. And they will most likely be infecting any local cats as well.
Either way their prognosis is not good if left untreated.
If they belong to the house owner then it is his responsibilty to sort them, or contact a cat charity (if in uk Cats protection league) they will often trap the cats and treat and neuter them and also test for infectious diseases.
Good luck and hope you manage to sort them in some way.