Private rooms and changing Grand Companies?

Apologies if this has been asked and answered before, but a search of the forum didn't bring me a result that helped.

I want to change my Grand Company so I can do Frontlines with my friends, but I want to know what will happen to my private room first. One of my Free Company members recently tried to purchase a room of his own but said he couldn't because his rank in the Grand Company he was in wasn't high enough, so that made me hesitant to make the switch.

What will happen to my room? Will I keep it since I already had it before changing Grand Companies, will I lose access to it until I rank up enough to "earn" it again, or will I lose the room, the 300k investment, and all the items (including non-removable things like walls, floors, and ceiling lamps) stored within?

Are you sure he didn't mean FREE company? If you are the highest max and switch to another gc nothing will happen.