Ours had a wooden playhouse that DH converted . It belonged to the DC and was on a wooden sturdy base , there were four windows , 2 could be removed and the space was filled with bars+chicken wire and mesh to keep everything big or small out . The windows bolted back in place .
They had a big haybox (or two depending on how many we had) with access out onto the floorspace .
In winter we gave them the small bedroom which had no door and we kept the radiator off . They had C&C / big cage .Again depending on the groups .
Indoors or outdoors they need protected from damp, extremes of heat or cold , draughts , changes from hot-cold or cold-hot . Predators -cats,dogs,foxes
They are messy little gits and the hay smells . Ours were never able to go more than two days . Daily cleaning worked best , roll up the dirty newspaper , lay fresh and fresh hay . Proper clean weekly .
The hay gets everywhere !
And they are noisy . For such prey animals they were quick to tell us they were starving . Walking down the garden with their supper we could hear them squeak .
In summer they had big rabbit runs secured with heavy tent pegs , not open topped pens .
They loved being out but need to be secure and protected and of course the fixes are round at dusk .
They are gorgeous little creatures but hard work and you need to be checking for illness as they hide it .
I used to love emptying the piggie house , cleaning it , replacing the flooring and re arranging their houses . Lots of fresh hay .
They'd come in from a hard days graft ( eating grass) hungry for supper , think "When did this happen, we didn't leave that box there " before turning my beautiful clean pigshed into a sty in ten minutes 