I need a base calculation for starting. How about BTC price will be fixed and I have free energy? Can you make a suggestion?
Huge problem right from the start - BTC exchange rate is very far from fixed! Typical daily changes can be several hundred US$ and over the last 2 weeks it changed by almost $2k
If you have free energy
AND CAN REMOVE THE HEAT AND DEAL WITH THE NOISE then BTC price does not matter too much because you *will* make money. How fast you make money is a different matter.
Why do so many folks overthink this?
All that matters is the same for any business: Subtract cost of rent and utilities from gross monthly income. Apply a percentage of what is left to paying off miner. What is left after that is Profit.