All this stuff sounds pretty interesting. Any beginner-friendly pointers on any of them? Especially the last one (how to get started, minimum amount of money for it to be worth doing, etc.).
As for the actual yield on loans, there is no lower limit beyond the fact that there are fees to lend and return your coins to and from these lending contracts. Those fees are currently quite high, so it is in your best interest to plot those out when calcuating returns.
