Age doesn't matter (at least not for older buns,babies are less likely to train well until they're older), althoughpersonality and hormones do. Fey and Sprite were 1.5 yearsold when I got them and had never seen a litterbox before.They took to it really well. They're not perfect, but I caneasily sweep up the odd poop on the floor.
First things first- if your bun likes to pee in a particular spot,that's where the litterbox should be. If he was two spots,use two litterboxes. Second, hay! Put hay in thelitterbox or in a hayrack above it. Rabbits like to eat andpoop at the same time. Third, put a few poops and aurine-soaked paper towel in the litter box to give him theidea. Fourth, clean up urine spots outside the litterbox withvinegar so he can't smell them and think "Hmm, this is the potty place!"
Usually spay/neuter helps a lot because intact rabbits tend to markterritory. But 5 years old is getting up there to do anelective surgery, although many rescues and shelters neuter olderrabbits without too many problems. If you are interested,make sure you find a good rabbit vet get lots of information from him,as well as an extensive health check.
Have you had a chance to check out Bunny 101 yet? There's alot of threads there on topics like bunnyproofing, feeding rabbits,litter, cages, toys...
Here's the thread for bunnyproofing for starters:
http://rabbitsonline.net/view_topic.php?id=12079&forum_id=17
