Coop: subdivide and rent

So long as you will always be residing in the unit yourself, you've reduced if not eliminated your potential headaches with the building. Whether you are sharing a bed with a partner or sleeping in different beds with a roommate shouldn't be relevant. Similarly, if an intimate partner were to pay 1/2 the cost of living with you, no one could say anything about it. Situation should not be different with a roommate. This is obviously very general advice. Best to pose this specific situation to your attorney asap.

I think depending on the building, it's a real problem. What if the board foresightedly figures out what you're going to do and doesn't approve the wall installation?

In your situation, you should consider buying a condominium.

ali r.
{downtown broker}

I have a pressurized wall in a coop. The board probably won't ask you what it's for, but if they do, you can just tell them you're turning part of the living room into a home office or something. Since the wall isn't technically attached to the apartment it's treated more like furniture. You'll probably have to submit a rough sketch but you shouldn't need an architect's drawings. I don't think my board even looked at the application, I think the management company just wanted to make sure the wall company was insured.

A couple things to think about:
Be sure to ask for sound proofing or muffling of some kind. Otherwise it's just the metal studs sandwiched between 2 pieces of drywall... and you can hear everything. I'm guessing they could use Quietrock sheetrock or insulation of some kind.

If you plan to have a rug or carpet inside the room created by the wall, make sure you tell the guys to hang the door high enough so it clears the rug/carpet when the door swings open.