When the network goes live, Safecoin isn't implemented at first. This will take some months. So you'll be able to use the software as a test for free. When Safecoin is added, the MAID out there can be switched 1-on-1 for Safecoin. So in the beginning, only these half a billion will be inserted in the network at random addresses. When the Farming starts (with Safecoin live) it won't be that different from Ethereum where new coins are created every block. Only on Safenet they are created when someone Farms 1. And they're destroyed when someone buys space on the network to PUT data. The destroyed one can be created back when someone Farms that address again. So the growth is limited by the fact that coins are destroyed (no owner of the address) as well.