Basically Gamestop offers this same service, but essentially it's free. They have a 7 day return policy on all used games. This means rinse and repeat.
What you need:
I'll give you two different scenario's:
1) You heard the new Wolfenstein is pretty dope, but don't want to cash out $30 to play it's 10 hour campaign. Simple. Spend $30 on the pre-owned game. Beat it within a week or 7 days and return it. You have the option to either get your money back or exchange it for a different game. So let's say you want to exchange it for Titanfall which is $10 used. You would then get $20 back in cold hard cash. Essentially you need money to play games, but you'll get your money back in a week and you'll get to play the game as if you rented it. In the end it will cost you nothing.
2) If you own a soft modded wii with any of the applications like wiiloader or usbloader you have the option to download those games to your console. So you can 'rent' a game, then return it the following day. You keep the game and you keep the money. Free games forever. I can get down to that.
So why would you ever purchase a new game again? Good question. If it's PC exclusive.
If I saved you any money at all, I'd love some credits. But again this method is free and completely legit, so you don't have to give me anything.