Bitcoin can be said Passive income basically involves bounties and airdrops, and much more, but the bad quality of most coins means ideally you should immediately convert any revenue from this into btc directly. Sure you can lend your bitcoin, but it is not recommended due to various confidence issues. Indeed in following the bounty and airdrop usually scam / coin has a bad value. more thorough in following the bouty ICO.
It is always depend the passive income type that you are talking about, and the country that you live in. Why ? That is because I believe in every country has their own law and their own economic condition. If you are talking about mining, than that is good. As long as you know the way, as long as you have enough money, as long as you have a propriete hardware, as long as you have the right electricity to pay, and as long as you have the right environment in your country. Mining can be good income if you put it in the right place. And now, I believe that you already understand what I am talking about in here, and right now, hahaha.