Plus, many other aspects make its much more complicated. 

What are some ideas on navigating this zoning complication or would this be a safe purchase as is?

The income/expenses with this place were a little complicated Due to the floor plan of the building so I had to get a little creative.  

To make it more complicated every county has different valuation processes and different equations to figure the taxes. 

It is more complicated, but it gives you more power and less risk.

Granted that would be a year from now but doesn't hurt to be aware of potential complications in the future

The firms focus is in commercial property and I have learned an incredible amount about navigating city and county regulations, dealing with complicated leases, permit running and expediting and so much more.

I wouldn't be putting any money into the deal, just the time and know-how (such as it is).Complicating the issue is he has a brother who is potentially interested in kicking in money as well to make a deal work.So how do I structure this?

For your example we'll need to make it more complicated an make some assumptions along the way.Scenario 1 Assumptions1 - You pay out of pocket the entire cost to build your ADU, cash invested $100,0002 - The value of the property does not justify the fees associated with cost segregation so you will use a 27.5 year  depreciation schedule.

If I add an ADU in the back, having five or six cars would be a bit more complicated..