I was saying that there is no guarantee of the return of the investment. Did I understand correctly?
It all depends on what warranty you talking about.
The only numbers we can warrant are from blockchain math. They hardcoded and unchangeable : 280*0.75 coins reward each 120 seconds evenly distributed across masternodes. So from this PoV you may feel safe. Earlier you get in, faster you'll mine. Say with 1 masternode in network you will get 21 000 PDX in return from 20 000 PDX in roughly 100 minutes.