If it does not cost anything to produce a PoS coin then it does not cost anything to attack the network. As a result any PoS coin can be attacked for free
Yet another with no idea how it works. If it can be attacked for free how are those coins surviving? Take a look at Coinmarketcap, the top list is dominated by non-PoW coins. Surely, if its that easy they would've been attacked by now - the incentive is there.