I am a little confused to answer your question, because you want to earn money without investing money. Actually you have done one way correctly, that is by mining. Well, I think there really isn't anything that is obtained for free without sacrifice. There might be another way to get free coins, that is by participating in bounties and airdrops. Thanks.
There's no free in this world buddy, if you want to earn you gotta invest something like money otherwise you won't get anything in return, if there is a way to earn without investing everyone would go for it.
you would want masternode if you want to earn without that much effort, while your holding your coins you also get more coins by holding possible more profit in the long run if you sell at higher price.
Why do you think that ONLY mining brings benefits to the network? On the contrary, I consider this a monkey- activity that damages our planet.
I have already written that I have two full nodes, and I bring this benefit.