I think that building up your passive income with Bitcoin and altcoins, is a whole lot easier than doing marketing, clicking ads, and others. Since cryptocurrencies are highly volatile, you can make use of that volatility to build up your passive income along the way. In addition, staking, lending, and holding coins into your wallet, can lead you up to many ways of making your passive income grow with minimum effort involved. Just sharing my thoughts. 
But a passive income must be some periodic based, it could be weekly or monthly basis. Only lending out will fetch such opportunity but when considering the defaulters and scammers I am not finding a smooth income generation through it.Staking, I have tried but only very few coins hold their price levels others losing their value along with new block rewards. (People keep on selling their staking rewards and no buyers to back up).
Holding coins for value appreciations will not guarantee for regular income.