guys, don't get too technical....
in English and for the computer/technical illiterate
CPU = Rig....(yes...entire rig)
At $2 per day it is likely he will never recover his hardware investment unless he has access to free electricity. To clear $2 a day he needs something pretty substantial. At that point all you have to do is go to a mining profitability calculator and plug in your variables and go from there.
if he has free power and makes the right rig he could do okay.
but you are correct no free power = not very good
here are some used rx 580's
https://www.ebay.com/itm/SAPPHIRE-AMD-Radeon-RX-580-NITRO-4gb-11265-07-20G/263941946731?130 each buy 4 for 520 cheap power they should make what he wants mining xmr