We have a 2009 Sydney Outback TT. Over the years as our family has grown from 3 to 5, we've had many friends stay with us in the camper, and their families have grown as well--too small now for two families even though it sleeps 10 (queen air mattress in sofa, dinette makes a double). Everyone we've camped with has loved staying in the camper so we are going to do the same thing as you, setup our camper as a private guest house for visiting friends and family. It has a queen master room, 4 bunks in the bunkhouse, tub, shower, toilet, fridge, AC and heat, HDTV and DVD, stove, range, running water. Should be nice and easy to stabilize on a concrete pad which I'm assuming would be one of the only complaints (rocking) aside from people not flushing the toilet properly and letting a bit of bad air back up inside.
I personally think it's a great idea and as a bonus you can take it to the mountains or the beach aside from giving visitors their own mini-house.