1: If you have a life, it won't be profitable. You have to be able to spend time troubleshooting, reboot when something happens, setup/takedown/sell, impliment cooling... It's a lot of work. Not to mention, if you're away for a few days and a machine goes down, there goes a ton of your profit. God forbid a piece of networking gear goes out
2: If you're going large scale, you need to think about the possibility of something going wrong. You're not a datacenter with fire suppression, and you're working with a ton of power. Spoondolies can easily happen to your house. Insurance would negate any profit
3: You're a residential house using a ton of power.
This could easily be you
4: Power for the machines =/= power you'll use. AC is expensive both to implement and run
5: Power strips to take advantage of your full capacity will cost a lot
6: If power goes out you're screwed. Got a storm? There goes your profit. Same goes for internet.
Enjoy mining yourself, fill the room to your heart's content. Don't try to make it into a business