We bought it back in 2015 without knowing that there was an un-permitted addition where the carport had been turned into another bedroom/storage room.

What my wife and I ended up doing is remodeling the house with an addition and converted the garage into an Accessory Dwelling Unit (permitted and rentalble guest house with separate address and electrical meter).  

If I had to do this over, I think I would have checked with the town to see if there were any open permits.

Hire this out right away either way.Then analyze the numbers and make sure this is a solid investment.Also make absolutely sure a STR is permitted and their is no talk about them being banned.

We had successfully bought out four of the five units, received our building permits, and assembled our construction team.

I strongly doubt they have had a survey done, and the permits for drilling a well and a septic field are probably outrageous.And wait until the tax bill comes.Maybe you should wait until they build a Home Depot up there though.

- on what kind of notice will this be permitted- does the other have 'first refusal' to take over the whole venture?

I use a plumber for plumbing, electrician for electrical, but who is able to pull permits for window replacement?

I was wondering if anyone could recommend an investor friendly architect to help on a gut rehab project (design, plans, permitting etc) in Chicago?

With the planning and building dept's heads deep up their rectums plan for 4 years to get your permit.