I'm not really sure if that's really possible passive income that they earn, just like other said, it's not a regular bank stuff.I see with what you do, this is a long-term investment, and this will upset you, and always want to know that the coin has gone up or not, and you are always curious, my suggestion you better.
I think we can generating passive income from the cryptocurrency especially if we have bitcoin and many altcoins because each price of the coin will increase higher in the long-term. so I think if they can have many coins from now, they are making a lot of money in the future. I don't think that they will upset especially if they decide to invest for a long-term because they already learn and know that in cryptocurrency, they can make money in two ways which are short-term and long-term so if they go with a long-term, it means they really make a lot of money in the future. and if you can learn from the history of bitcoin, from 2009 until now, how much percentage that bitcoin could reach? but this is for just people which really believe with bitcoin and not underestimate in bitcoin and they still hold on tight their bitcoin for a long-term.