I drive a '12 with base trim and manual, which is the same car you are looking at. My experience (at 42000 miles) is that it is solid, no worries car--albeit I was coming from a '98 civic. Does seller have maintenance dates/miles written down in the manual, or some other records? If s/he did the maintenance when indicated by the car and your mechanic signs off, you should be in good shape.
As for cost of owning/operating, if you drive prudently, you'll far exceed the epa estimated MPG. Over past three years, I get 41-44 on my commute (50/50 highway/city), but definitely working to get that. Long road trips are closer to 35 MPG (still higher than epa), as I set cruise at 75, rather than put along.