Unpermitted addition in Phoenix

[Yader Gomez]

Hello all,

I just went under contract for a great property with two homes on the lot and I plan to owner-occupy for several years. The zoning is in order, separate meters, good neighborhood. But it turns out that the master bed and bath for the main house (where I'll be living) is an unpermitted addition. This helped me get the property at the price I did. 

However, I'm concerned what this means for me going forward. Everything I've read after looking through tons of previous threads suggests that it's not much of a problem if disclosed (which the seller did), not counted in the sq ft of the property when considering the sale price (which they also did correctly), and is also less of a hassle if the property is intended for buy and hold as opposed to a flip (which I plan to buy and hold). 

My main concern is for the distant future when I intend to rent this front house out as well. The master has windows but they're high up and small. So in order for me to get a permit for an egress window, the addition itself needs to be permitted I'm assuming. I'm no professional but at least to my untrained eye the construction looked solid. What are the steps for me to get this permitted? What can I expect the costs to be for best case scenario of hiring an engineer and getting the city to grant a permit? I assume the costs are a nightmare in the worst case scenarios of a either a major rebuild or full teardown of the addition. Any help is appreciated!