In my experience, if you see one rat, there's dozens more that you are not seeing. And rats are destructive. They are able to chew through concrete. KILL IT! (Just my opinion) Don't re-locate it to make it some one else's problem.
This is true about them being able to chew through concrete.. I've seen it! They are so hard to get rid of.. we had two HUGE black rats here that chewed through the foundation of the house. Doesn't even sound believable, but it's true!