If you would like to earn some money through the domains you are not using for now, you can park the domains on the domain parking sites. There are some domain parking sites which will park your domains and will get some ads displayed on those domains. If a visitor lands up on the domain and clicks any of the ads, you'll earn something out of it (though, you shouldn't expect the amount to be high
).
This would be a good option to earn atleast some amount of money which can actually be used while renewing those domains
