I'm envious of the basement daycares!! My own is on the main floor of my home. We have dedicated the diningroom to the daycare, and use the livingroom as well, as it's one big space. This is the room with the family piano and a small TV. It's smack in the middle of my home, but there are benefits too...access to the kitchen, and the mainfloor powder room. I'm not one for portable potties and prefer to train on the real thing, so that makes it easier than my basement.
It would be nice to use the basement though, and be able to use the side door! We have 3 rooms down there and the basic plumbing for a bathroom yet-to-be-put-in. But, it's the only place I would allow DH's big TV, and I hate how it takes over the room.

ETA: They nap in the spare bedroom. We have a toddler bed and a number of pack-n-plays. I'm thinking about getting some cots for when the toddlers turn into preschoolers.