After closing I think he found some old dry rot some where and began tearing apart the the wall. 

Since I plan to hold this property long-term, I don’t care about increasing official square footage, I just want a functional space.Question: Has anyone here done a “garage upgrade” or ADU extension like this, pulling permits for essentials (bathroom, electrical, replacing garage doors with walls/windows) but keeping it simple otherwise?

Quote from @Julian Hendrix: Quote from @Jaron Walling: @Julian Hendrix How much experience do you have with REI?"

This is the lowest level since September 2024, putting rates today back in line with where they stood a year ago.For some broader context, here’s a chart for 30-year fixed mortgage rates over the past 5 years:Even with mortgage rates beginning to ease, affordability has not meaningfully improved, and a recent Wall Street Journal article breaks down the broader forces at play.

Also, I'd check A/C unit -central vs in wall - central will be more expensive to fix/replace vs in wall unit that can be swapped out easily as DYI.

Remember, they will need hand supports so if you tile the walls make sure you save extra material to replace where you need to make holes for the supports.

Especially since you will not be present to make decisions quickly, sign off on change orders, assess the situation when the walls are opened up and the scope of work increases, etc. and that makes you more difficult to work with than someone who is local. 

At the worst, we took out that section back to the wall and re-installed new planks.

My framer said that it shaved a day off on the walls alone.

Those quotes can be fair for a 4‑zone retrofit without ducts, but only if the scope is apples to apples: line-set lengths, BTUs per head, brand/warranty, electrical, condensate pumps, permits, and wall patching.