Usually, you pay a hefty price for free electricity (like in dorms etc): Noise Heat
You're gonna live and sleep in all that, remember. Having those fans going 24/7....
Believe me, electricity is not free at home when you start mining with a few S7s.
Was about to write the same. Had some Scrypt ASICs in the sleeping room for some months, it was a real pain.
Additionally, like he said, energy is never free. Maybe for you, but I doubt your family will be happy to get a huge energy bill to give you free energy for mining.