The concept Ned Carey is discussing is called the Statue of Frauds.

They are brining the land and some construction bids to the table.I worry less about agreeing on marble v. granite but protecting our individual interest from things like future liens etc.

Go by that statue to law, know them well.  

The ADU will be treated as a "feature," like a hot tub or giant unicorn statue.

If it's a small house, you need to completely redo electrical, plumbing, mechanicals, roof, siding, etc, and want to use granite and marble throughout, you're probably in the $150-250/sf range. 

Stay away from Marble, Granite and Concrete counter tops!

Rich people giving other rich people statues.

But if it is more contemporary you could go with quartz and granite, or quartz and stainless, marble and stainless is really in too.

Each state has different legal statues.

It feels like money flushed down the drain because the carrier holds all the marbles.