Basically my Seller just needed $6K more because a Buyer's Agent wanted to get paid an extra $2K. 

Like if would be the same thing as then paying us monthly and we just have extra assurance that the money is there?

So if he finishes X days earlier, than you pay him an extra $X.

We calculated the collateral value of each property, and told him we would be willing to do a release based on (1) a payoff of our estimate of that properties collateral value PLUS (2) a extra fee (profit) to us of $50,000.  

I like to think our company goes the extra mile to maximize bookings and revenue for our clients.

The reality is the opposite - if it's not in writing then the PMC doesn't have to provide the service or can charge extra for it!

I would argue that you can only save a finite amount of money when aggressively paying off the mortgage, but you have a much higher potential increase to your assets and wealth by taking that extra principle and reinvesting it into other investment instruments.

While rent rates do increase, so do the potential headaches of managing multiple tenants.For example, here in Bryan and College Station, TX, you can get an extra 10% by renting out rooms individually.

If you want to shield yourselves as the owners of the properties, then I guess it's possible, but not sure why you want that extra accounting headache.  

Just be prepared for extra coordination and make sure you have clear agreements in place.