I have chickens in my house,they are in a mud room off my kitchen. There is NO smell,i clean their area daily. They go out in the summer,but if it is very hot,they come back inside where there is A/C. Any animal will smell if not looked after properly,this applies to all animals not just chickens. My silkies do not like the cold,they just stay in their coop,inside they run around and are extremely happy.
So yes, you can keep chickens inside,just make sure you have at least two,they do need a friend.
In my opinion there is nothing more smelly than a cat box,and that is cleaned daily also.