...The only question - for each specific coin you need to have some minimum amount in your wallet? Where to know?
This is different in all projects but in the majority, you can stake each amount available.
POS is a great way to earn coins with no high cost for equipment and is easy to manage. One just runs a wallet on a laptop or even a Rasberry Pi and is enough.
Is a really not expensive way comparing to POW where not only equipment costs a lot, but is time and resources hungry. Don't mention the heat, problems and knowledge needed.