Start off by building a computer that could cost over five thousand USD. Mining has pushed up the prices of a decent graphics card and you need ten of them.
When you've finished spending all that time and money you get to see your electricity bill spike up to ten or motre times its usual level.
At the end of it all, the fad falls over and anything you found is worthless. The reality is that the people who were going to make any money from Bitcoin or Etherium have already made itand got out.