This contract provides for great monthly cash flow, but it ends after 60 months. There is no principal to be returned because the mining computers will have significantly decreased value.
If the price of Bitcoin drops, the return could decrease. At a price between $20,000 and $30,000 the return is between 4-5% per month. If the price falls below $10,000 then they could pause mining as the returns do not justify the cost of electricity.