We have had indoor piggies and a cage like this one on a sideboard in the living room but I'm not sure it was actually big enough, we are thinking of getting more piggies but this time want something more like this one.
For the past few years I've either had 2 boars or a boar+2 sows. I've tried all sorts of indoor/winter housing. We started with a 4'x2' plastic base/bars on top ( soon to be known as The Hated Indoor Cage) but my boars only tolerated it if there were 2 hay boxes. We tried a run (made of panels) on tarpaulin with cardboard/newspaper A C&C set up but they crammed themselves int a washing basket (2 cut out doors) full of hay...............so back to the Indoor cage.
Last winter , the boar+2 sows had wooden litter (rodent safe) newspaper, fleece and hay cookies. Changed the paper/fleece daily.
This year, I have 2 more sows who haven't bonded with the trio.
We keep them in the small bedroom, so I think I'll do a 2 level C&C ( one level each group) but I haven't worked out the sizes yet.
The hay is the messy bit so I use those solid discs, they have proper hay in the outdoor Pighouse so they can be as messy as they like there They can be noisy at night, I throw an old duvet over them, works for parrots, not for guineas