You MUST use an enzyme cleaner to clean up anything kitty pees on. We use Nok Out (http://www.nokout.com/odor.html
) - in our experience it works much better than Nature's Miracle. But even with this sometimes we've had to apply it twice.
You must THOROUGHLY soak the area - down to the floorboards underneath. Cover the area with aluminum foil while it dries. If you've soaked it well enough it make take 2 - 3 days to dry depending on your carpet and humidity in your apartment.
Do buy the cat attract - it works. It's expensive and you need a fair amount of it, but if you can afford it, do it.
Next, invest in a cheap black light - they're available with batteries, which makes it easy. At night, investigate the hall and your apartment with it. Urine will show up as a yellow splotch. Make sure you get every spot.
The aluminum foil will discourage using the same spot.
But if kitty is peeing outside of the box and it's not a UTI (BTW - our Tuxedo did not have a UTI, but turned out there was a "cyst-like" bundle of crystals embedded in his bladder wall. The MRI at the vet wasn't strong enough to see it, and we had to take him to a specialist before this was found. It required surgery. But his problem was NOT a habit, and the surgery cured the problem. We then had to put him on a special diet), something is stressing him and you have to identify that problem.
Maybe he needs to be played with more. Add 10 minutes a day. Maybe he's seeing a cat out the window, and it's a territory thing. Invest in some Feliway spray. And the play will help diffuse the frustration.
This last time our Spooky had a peeing-outside-the-box problem, it turned out she was trying to tell us she was in pain. She had two bad teeth that needed to be removed, and when she had her dental, they discovered this. Funny thing - they removed the teeth, and she stopped peeing outside the box. So if he didn't have a full physical, maybe consider that. It could be a different problem, not just a UTI.
Maybe he doesn't like the litterbox? If it has a top, remove it. If it doesn't have a top, maybe try getting a box that does have one. In fact, I'd invest in another litter box anyway. Sometimes that alone solves the problem.
When Spook first had the problem because of stress, we put the litterbox where she kept peeing. We slowly moved it across the room to where we wanted it ( about 6 inches a day). It was a pain in the butt for a few weeks, but that worked.
Also, for avoidance of areas, you can try oil of olbas instead of citrus. Health food stores should carry it. Drop some on a teabag you've soaked in water, and put that out on the aluminum foil. Shouldn't need it more than a week or two.
Most importantly, remember that he's telling you something, not trying to anger you. You just have to keep trying different things until you discover the problem.
Many people are adverse to using mood altering drugs, and I understand why. On the other hand, if you reach the point you're at wits end, and you're absolutely certain you've ruled out any other health possibility, talk to your vet about using elavil. If it's truly a stress-related problem and you can't discover the source of the stress, a low-dose of elavil may help everyone find some relief.