It really doesn't matter. Successful startup X could have began in a coffee shop, apartment, dorm room, open office...it was still going to be successful. People with the right drive are going to create and be productive despite their working environment, not because of it.

It's only later on in the process when the company can buy office space and do some hires, when people start to get picky about where they work. I've had some of my most productive days on a borrowed old laptop and a folding table in a breakroom.