Mine had my DC old wooden playhouse , like one of those little Swiss Chalets .
DH altered two of the windows so we could take them out but inside the frame had a bars/chicken wire and mesh lining to keep out large and small predators and flies .
We gave them hutches on the floor that had openings so they could get out on the floorspace 24/7
It was dry , we put rubber mats and cardboard on the floor
Changed the bedding in the hutches every day
In Summer they had a fan
In winter they had a heater to take the chill off and SnugglePads in deep hay
There was a light to make things easier for us .
In Winter they did come in at night , in the small bedroom.
We had to make sure the Pighouse was warm enough and fresh bedding before they went out .
Usually bring the pigs in, take out the dirty bedding .
Next morning ( usually me
) put the heater fan on to waft , fresh paper/hay , leave 30 minutes , put the piggies out with breakfast .
They loved it , loads of space and light .
Indoors they are messy little rodents and noisy 
When we got to the last 3 oldies we kept them inside all winter , we reckined they were too gragile by then to ive out . Had to make sure the radiator was off in their room.
They can be easily ignored though and you cannot afford to do this , they can get very ill very quick .
DD and I did the PigWork , we shared the guineas