I just meet this guy and spoke with him.
He said they have this farm in Norway which has free electricity thanks to geotermic and eolic energy.
So I do think that if a farm is mining coins and selling them every night, and it virtually has no expenses apart from employee and technician, it could be the case you get back your capital ?
As soon as you hear the word guarantee, you can "guarantee" its a scam. Not in one single market crypto or not can you get a guaranteed 20% return each month. The scams wont stop until people stop putting money into this stuff. Your buddy is 99.9% in a ponzi (.1% chance the company actually believes they can deliver 20%). If you are a friend you will push him to get out asap
Same goes with trading...i dont care if they guarantee 1% in a year, you most likely will lose 100% of your invested funds