Next time I go looking for a job, I am going to interview the code too. I am getting too old to struggle years to find my way around 200KLOC of undocumented code. It takes too long to start becoming effective. Of course, getting on a new project is another possibility.
It is a nice contrast, I have a day job with no documentation and few comments, and a side project translating Java to C. The Java code has fairly complete JavaDoc comments, good additional comments, and some additional HTML docs. Finding my way around it is straightforward.
The day job code probably will take 2-3 years to really know my way around. Of course, if I split, that knowledge goes with me. This product is just hanging on and needs new features, bug fixes, and visible progress to stay alive. There will probably never be the time & money to really document it. I expect this is a description of a project that has already entered its death spiral.