Definitely go for a building with enough space to host meets, exhibitions, open houses, all that stuff because that is how you bring in money and customers. Another thing to consider, good lighting! When a family comes to look at your gym, their overall impression probably isn't going to be as good if it looks like a dungeon. I know that alone kept me from a gym when I was investigating as an athlete. Bright, colorful gyms are always more welcoming and look more "kid friendly".
Develop a goal and mission statement for the gym. Let people know what your gym values, what you're working for, what is important to you and your employees.
Look for a place with room for birthday parties. Either a separate room, balcony area, or space out of the way of the equipment. That's another way to pull in potential customers, get your name out there, and increase revenue for the gym. It's not the teams that make the money, it's the solid rec programs and "fun" stuff.
For when the gym is up and running, think about hosting an open house during the first few months. Advertise at schools, family events, community centers, anywhere that could have interested individuals/families. At the open house offer some special perks (10% off classes, free t-shirt for registering, waive the registration fee, that kind of thing) and just let people look around the gym.
Contact local school cheerleading teams. I'm not talking all-star cheer type stuff, but local high schools. A lot of girls, at least in my experience, are interested in coming in for an hour a week to work with specially trained gymnastics coaches on spring floors, tramps, all that good stuff. If the high school coaches are willing to pass along the info to their team you could get a few girls pretty quickly.
It sounds like a great opportunity for you and like you're well on your way. I wish you all the best!