re: "free power"
Do be aware that all large miners are both VERY HOT and LOUD. For all intents and purposes they are very large heaters that convert all power fed into them into heat out. Only difference is that yes, depending your exact circumstances they will be very loud and hot heaters that pay you more that the electric costs. (in your case free). Considering that most of the new big miners take in over 2kw and many over 3kw think of them as giant space heaters. Can you deal with the heat?
As for sound: Earsplitting is a good way to put it. Some do have a lower power mode that cuts it down but still are loud. Think a loud blow dryer or vacuum cleaner loud.
If he could find a whatsminer m10 set to low speed it will use 1200-1300 watts and mine at 20th
20 x 0.00002 x 30 btc is one month of mining. I guess about 100 to 120 usd.
It will be okay for noise not terrible.