Do POS Coin really earn you a passive income ? I don t think so.
Yeah you get X % of the coins you hold added to your Account , but because everyone who is holding the Coin get s X % the total circulation will grow by X % too. So your share of the market cap does stay the same. So you you get more coins , but the value of each coin does go down. Like any other crypto , the profit does come from a increase in Market cap.
I would recommend you to have a look at TenX Pay token , because they could give a real passive income , because they pay a share of the companys profit as Ethereum to the Tokenholders.