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.

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

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.

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? 

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?

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

After moving out, we re-stained the front porch posts with a darker stain (photo is pre-stain), replaced the front door, did touch-up painting on walls and trim, installed new keyed-alike locks on front/back door, and installed a vented bathroom exhaust fan that wasn't there prior. 

Plan is to wall it off and convert to a 4br/2ba,  update existing bath and kitchen, new floors,  interior and exterior  paint.