So far, we have settled on the business model, market sector, secured the domain, and defined a few basic features.
What do we need to do? Continue defining more features while avoiding feature creep. We could then move on to the actual UI and layout, including a logo. After that, we would need to define a clear marketing strategy.
Am I worried? Not much. The service fills an existing need while having the potential of tapping into a much larger market - if you can make people happy, you're going to win. So, what's that little bit of worry left? Marketing. I don't care if a business has the answer to a "need" shared by the entire United States - if people don't know about it, they can't use it.