If someone says that you can make passive income from their project then you can imagine that it is going to be another scam.
Also in a non-cryptocurrency industry passive income exist, buy shares and you will get dividends.
I don't also believe the promise of a passive income. Yes, there are PoS coins, masternodes, but have you observed their market performance through time? Most of them decline after couple of weeks of trading. So I really don't buy the idea of passive income nowadays. Promising high ROI is really not true at all.
Passive income is true and exists in the cryptocurrency. If you search for POS coins, you will found that many coins could give you a nice amount for one coin, but you need to stake that coin for a long time.
For example, I tried to stake Bitbean, RDD, OkCash, Pink, Minex. For that coin, every day, I can earn some amount that still grows day by day. So, in the long-term, I believe that it will give me another profit because I can sell some amount I got from the staking to make another profit.
You can take a look at POS List. I hope if you are interested, you need to prepare some amount to start stake. But you don't have to buy a big amount because some of that coin allows you to stake for a small amount.