Hi Danw...i believe; bigger the better regarding the size of the enclosure....
Their; as you know, a large monitor......and ideally a reasonable sized outdoor enclosure,
would be the go. While it's small a large indoor cage would be fine; unfortunatly some people,
choose to let them spend their entire lives in such enclosures.....considering 'wild adults' have such large home ranges; and may travel several kilometres per day.
They are fairly easy to maintain...a varied diet; mine eating anything from catfood, lean mince, eggs, chickens, rats/mice...and rump steak which they turned their nose up at; after i cleaned the freezer yesterday...lol. I must say if your planning to get one; try to get a juv and put some time into getting it quiet. As adults, they canbe a handfull; and serious injury could occur if care isnt taken....especially at feed time when thats the only thing on their mind....which may turn out to be your hand.....having said all that; their awesome varanids, which i'm sure you'll gain alot of enjoyment out of keeping.