My general thoughts ...
I'm a wannabee space creator but even more than that I'm a wannabee coworker. Outside of a love of collaborating, my number one motivator is convenience. It is inconvenient for me to deal with the terrible traffic in the Dallas - Fort Worth area. It is inconvenient for me to drive away from work if I don't pack a lunch. It is inconvenient for me to maintain 2 automobiles... I'd rather walk or ride a bike or moped.
Traffic is the biggest aggravation for me by far, and I suspect for many commuters.. I spent over an hour going 13 miles today... along with thousands of other frustrated commuters. Plop a coworking space in or close to a congested area like my town (Keller, TX) and get employer buy-in, and people should be breaking your door down to use your space.
Convenience. Amenities. Employers willing to buy-in to coworking and/or self-employed individuals with a need. That's where I would start... so I would really think hard about traffic patterns in and around your target location.
Randy