HELP MY CAT!!!

Hello,
I have a cat and his name is Hendrix. He is about 10 months old. We
recently left him with our neighbors and upon our return we discovered
he has a strange discharge coming from his nose which is like a brown
color. The membranes in his eyes are protruding upward almost making
him look cross-eyed. He is very lethargic and is sleeping a lot. His
eyes are very runny. Our neighbors that we had cat sit, have a cat
and a pet rat. Their house smells really bad (like kitty crap and
urine) so it probably wasn't the best place for him to stay. At any
rate, we don't know what he may have or what to do because we are
broke from the holidays and our cat needs some kind of assistance.
Thanks