If the buyer has an objection to how much your making, ask him are you willing to take less profit on your end so I can raise my price to you when my profit is not going to  be as much as I normally get or want and your profit is going to be normal or better?

Don't worry about your first reply, I've been know to stick my foot in my mouth on may occasions, usually after to much alcohol though, JK, not really!

I normally allow extra children but not the other without an addendum. 

Normally when someone is doing something like this it has to do with a volume buyer, meaning he is doing several of these a year and his profits will add up all the way to as if he did another entire flip that year for FREE. 

Is there good foot traffic?  

Most states you cannot pay non licensed people kick backs for commissions.you can though just not charge what you would normally charge.so if your normal fee was 6% to double end and you wanted to only charge 3% nothing wrong with that

Then it would be a normal sale if you sell both sides you get the whole fee if not  then the split.

Do I normally invest the same amount or is there a reasonable fee I can include towards property ownership since I would be creating, closing, and managing the property?

Selling the house will enable you to have a substantial amount of reserves as a sort of solid footing to finance the vacancies for deals just like this one (no job required).Selling with the lease-option or selling outright seems to be the way to go.          

If I were paying a PM company, that would take 8 % of the gross right there, and voila: normaler numbers.