I want to provide access through the common wall of the two units of a duplex. nothing fancy, sort of a "doorway" without a door, same size of a door.

I plan to live in one of them thought it might be a good idea to use demountable walls instead of drywall to create extra bedrooms to rent out.

I'm not really sure why you are responding to my comment with this wall of text that at first glance appears to refute my position that GP's are to blame, but does not actually provide any argument.

And the customer service is super fast and helpful, although I should also mention you are often just sent a wall of text to read.

I'm exploring all options at this point including finishing the home with other builders, as well as selling what has been built (slab and block walls of a single family home 4 bed 3 bath) to another builder or investor.Does anyone have any recommendations on where to look for potential buyers for something like this?

You don't even have to drill holes in the walls to mount stuff.

Otherwise, anytime someone puts a small hole in a wall a landlord could use that as an excuse to oust them.

Is it a hard-stop wall, no more, or just each additional over the 5 would incur some per-envelope fee? 

Therefore, it did not make sense to foreclose on these assets, nor keep them at a surface.

I did this exact thing last time a tenant asked to install a TV mount on the wall of a bedroom.