Art wrote:

I would try to find out if that was once a legitimate method of building a
roof. If not I would be concerned about how the whole house is built and
walk away. I don't think your description of the roof can be accurate.
Shingles would not have the strength to do their job nailed directly to
rafters no matter how many layers you got. The first layer has to be
something special.

I'm guessing cedar. We recently sold a house we bought long ago with a roof
just like this. 4 or more layers of asphalt over the original cedar roof.
There were no problems buying then, or selling now, as long as the roof
didn't leak. That's all they cared about was leaking.

PRose