Like Poloniex sometimes offer trading competition or deposit bonus, you can join there and have some decent amount of passive income. I will not say that you may earn a good amount but a decent amount.
There are also some retroactive airdrops and genuine airdrops ongoing, you may find them in YouTube or Airdrop related Telegram channels. So that is also a good source of passive income. Another way is to join Bounties in this forum. You can visit
Bounties (Altcoins) board to see all running Bounties and can join them easily. Many people are generating a decent amount from the bounty payments.
But Remember one this all the bounties will not pay you or all aren't worthy. So do some research and join Good Projects.
Passive income and making money without cost are completely different.
Trading competition, you need to watch the candlestick and active for 24/7 because if you miss the moment, you will not win the competition or meet the minimum requirement to withdraw.
Bounties, you're need to post, retweet, comment, like, share, translate, creating content, follow, completing KYC which is you're working, not just waiting and you will make money.
If you have do some research, it doesn't mean you will prevent of getting scammed.