Seva means doing like him. ‘Him’ means the creator. He does everything for you and he doesn't expect anything from you. So to do whatever you can, not expecting anything in return; is called seva. There is definitely a payoff. There is certainly a return from that, but when you're expecting the result, it doesn't become seva. Without expecting anything, wanting anything, just do for doing sake is called seva.

Sri Sri Ravi Shankar