It can be feasible the problem is that as difficulty rises profits invariably fall so they will need to upgrade their hardware every few months to maximize the profitability of doing so
That said free electricity and a miner can beat selling it back to the system.
As for coins minted depends on the hashing power
The difficulty variable is tough for me since most of these concepts behind BC are fairly new. As i understand it the problem is multi-fold;
1. New more powerful systems coming into the market (if I understand correctly, that curve is getting less steep)
2. Commercial operators coming online with massive amounts of hashing power.
3. The code itself? Or does that go more to BC per block. (something about 2016)
If I understand the challenge correctly, the "life" of a rig could be extended using an APP that turns it on and off based on difficulty. Am I misunderstanding "difficulty"?
Additionally, I would assume that most homeowners would not want to purchase the rigs (some would), but I would propose that unused rigs (those in an area where it's no longer profitable) are leased to the homeowner. In this setup both the hardware owner and the "host" would share in the profits generated.