Buying non-permitted ADU?

[Account Closed]

My partner and I are in escrow on a home with an "ADU" in Washington state. After a competitive offer process, we had our offer accepted! Here we are a couple days later, and we just discovered that the ADU isn't legally permitted. This is a bummer - all of the listings say that this is a "home with ADU". My mistake was assuming that this implied that it was permitted.

The unit is built out of a basement conversion (the conversion itself WAS permitted), and it has the main components of an ADU - private entrance, egress window, kitchen and bathroom. It seems like the main changes would have to be separating the electric service, and I’m not sure how big of a project this might be. 

We're of course working with inspectors, the city, etc, to find out what this means for us, but I wanted to know if any of you had any thoughts or experience with something like this. One of my concerns is that we extended an offer amount that was higher than we typically would've paid if we had known the ADU wasn't permitted. We certainly won't close on this place unless it's clear that there will be a path to getting it permitted. Does anyone have any advice?