Since you have no contract, there is nothing that says you do not have to pay if you are not satisfied, and your spreadsheet would seem to indicate you owe him the money.Similarly, since you paid him for previous work on the spreadsheet, and the spreadsheet shows you owe him for additional work, your argument is not very strong.

A strong professional relationship should be able to handle honest communication!

This could be laborious as a one at a time deal.Not sure if this would work but you might be able to pay someone from Fivr to write a script that would do it automatically for you and generate a list based off of the multifamily addresses that you already have.   

There is a stats page on furnishedfinder.com that you can use to see what midterm rentals are asking for in your area, based on bedroom count.

The only good use I can see of the fees are based on rent charged would be for a tenant to purchase it and charge themselves $0 or near $0 rent to avoid the rent based charges. 

Good post with a few good ideas, thanks.A note about San Antonio, is that it historically has a big turnover in homes due to the military bases in the area.

Sounds like you need an agent and/or contractor based on your strategy. 

This is home for us, and our portfolio is based here.

If it were to read LP member owns XYZ% and will receive a certain percentage of proceeds based on property performance, that's a different story.

I'd probably stay away just based off that.