I was up on our roof for four hours yesterday, clearing the snow and hacking away ice dams.
When I had the snow cleared off the upper section, I discovered some interesting details.
This is a picture of the upper roof just above our trouble spot that's allowing water into the ceiling below.
Now, I'm not a roofer, but it seems clear as day that this section has been patched by adding a newer piece of roofing on top of the old roof. It's roughly 2' by 1' in size.
Here's another picture of the same section from a different angle.
Now, the trouble spot is at the ledge where the upper roof meets the lower one. There are roofing nails and screws which have backed out, and whenever there's the smallest bit of water forming on that section, it follows gravity and goes down the screw and nail holes. Here's a picture of where it seeps into the uncovered plywood of the vertical wall underneath.
We had the agent contact the seller, and the guy who sold us the place steadfastly maintains that a.) there were no water leaks in that house, and b.) he wasn't aware of any prior roof damage.
Once again, I'm not a roofer, but I have a sneaking suspicion that the seller is talking out of his southbound orifice, and that the inspector who looked at the place was certainly acting in the interest of the seller.
We typed up a cordial letter to the sellers, suggesting their cooperation to find an amicable solution. (Actually, Robin's original letters was more along the lines of "You motherfuckers...", but I toned it down a bit in the second revision.) There are more roofers slated to come out and give opinions and estimates, and we'll get the thing patched and then try to get our cash back from the sellers. If they keep disavowing prior knowledge of the roof issues, we'll sic the Dogs of Law, and take the whole thing to court. To my unschooled eye, it seems that we have a pretty good case for a "Failure to Disclose" lawsuit.