I have 2 questions - 2 different cats

Question
My first question is about a cat that has suddenly appeared on my front porch. About 2 nights ago when I came home, I saw a dark  figure laying on the edge of the porch. Thinking it was my yellow cat, I ignored it until I saw it up close. The poor thing was awful dirty, and it wouldn't stop crying while I was around. It had a stuffy nose, and when it meowed it sounded as though he had a hard time breathing. It also had fecal matter sporadically under his tail. He has approached me, but won't let me touch him. Occasionally when he meows, it comes out either like he is about to fight, or calling a mate... so, I can't tell if he is in pain. He doesn't stay around the house all day, he mainly just comes at night. Should I try to treat him, call for a shelter to come pick him up, or just leave him be?
My second question is about a cat my friend adopted about 4 months ago. He adopted Mimzy and Socks at the same time from a nice cat shelter so they have all their shots, litter box trained, and have also been neutered. A couple days after he got them, they both started using clothes, bed sheets, and the bathroom floor instead of their litter box. I did some research, and tried every solution I could to try to make them use the litter box again. I got a new box, moved the location, and change the litter to fine-grained. I also fed them food for a UTI. It worked for awhile, but then they started using clothes again. Is there any other solution?

Answer
Hi Anna,

The question you want to ask yourself is are you willing to spend what is necessary to take care of him? He sounds like he is in pretty bad shape. If you call the shelter they will most likely put him down. If you leave him and ignore him he will most likely die. If you take him to your vet there may be a chance that he can be taken care of. If he's too far gone at least he will be put down the most humanely way. Just make sure that you wash thoroughly before handling your cats. If he has a communicable disease you want to protect yours from it.

The number one reason for cats to change litter box habits is that they are sick. They should be taken to the vet to get checked out. Since feeding them that special food helped I would be inclined to believe they have something wrong with them. You also have to clean all the stuff that they used with a good enzymatic cat odor cleaner. They can smell stuff you can't and can be tempted back to using areas they shouldn't. Also check this stuff out; http://www.preciouscat.com/
Lousy website, great stuff though. You can get it at places like Pet Smart. This stuff should help. Let me know what happens. Good luck.

Ciao, Karen