It's not that easy there other overheads. Electricity costs and cost to replace a miner that fails. You need an area to set it up and keep it cool and running well. Then the time it takes to get the miner to your house is costing you for everyday you wait. You can also use your miner to heat up a cold room if you from s cold country. In that way you can get more out of it and squeeze extra profits you save bit using a heater. It's a great idea.