Being this is informal and not legally or correctly constructed in a formal agreement with the parties I would do the following : i would go over there ,smack my son right in the face for being a petulant insolent fool with my investment and then I’d march right into the building and tell his squatter punk roommate to pack all his crap and get out immediately or I’d throw it out on the street .

Maybe the more I learn about it, I won't be such a punk in pursuing it. 

I would focus more on the analysis/numbers than the aesthetic.

But again, that's an aesthetic and budget choice.

Courtney, working as a licensed GC I have done this many , many times but if you take it from me it is easier and more aesthetically pleasing and useful to simpley have plans drawn up , approved for building permits, and build a new third bedroom.

I'm great at money/math/analysis (my day job, senior analyst with 14 years exp), and my wife is a very good creative with an eye for design/aesthetics. 

Clean plate ware, free of designs can add to an aesthetic appeal and add a tidiness to your modern kitchen.

More than likely It isn’t going to get any better with this punk .

My wife and I fell in love with our first flip and made very little off it because we were more interested the aesthetics than the finances. 

When I walked the comps this was a no-brainer for me and with Zerik's design aesthetic there was no doubt you would hit it out of the park, now shut up and take my money!