Need board approval for roommate in Co-op ?

I have an opportunity to buy a co-op that I liked, but is on the higher side of my budget. I have a study/second bedroom that I can rent out to offset some of the cost. I understand that by law, anyone can take a roommate in NYC for any reason and no one can do anything about it." Question is - does this apply to co-ops? Is this considered a "sublet" if I am also living there? What happens if I have my gf moving in with me? I will ultimately ask the broker if the decision to buy depends on it, but don't want to raise unnecessary "red flags". What is the experience of those already living in co-ops? Thanks!