I am building a vertical addition above the existing main level which would have vaulted ceilings OR alternatively the front half would be vaulted and rear where the bath/closet is situated would have flat ceilings with rooftop deck above.    

It’s called “flat rate” billing.

I recommend you add a little more detail to this post.. what kind of property etc etc.I have done probably more than 12 to 15 deals in south side all 2 to 4 flats.. at first they all sold to investors the last 3 or 4 sold to owner occ. 

I also when things were hot before interest rate spikes I just followed what Lennar was doing. they had a flat fee of 5k.. which for thier product was basically 1% buyer agent fee.. my product was / is 700k plus so  I was just posting 9750.. flat fee and had no problem with agents bringing in buyers . 

Detached ADU behind SFH, on flat ground with excellent access, in Adam's Point/near Lake Merritt. 

To avoid all issue we charge a flat fee to both tenants and we pay the bill.

Most property manager cover all the services you offer charge a flat fee of 20% gross revenue. 65% is exorbitant - its 3.5X the market rate.

My wife and I own a two-flat in Chicago, and we're planning to upgrade our heating system.

What are Best Practices for Agent Remarks when Listing property with a Flat Fee Broker?

This is either splitting it or a flat fee.