How do you plan on gaining national coverage of listings? Between the agents, brokers, aggregators, and MLSs the data supply chain is incredibly fragmented. Securing access to all of this data is an incredibly time intensive process that requires a LOT of relationship building. Unless of course you try to go the 'redfin' route and become a licensed brokerage in every state... but then.. you lose your edge and you're essentially competing with Redfin.
How do you plan on getting all of that listing data?
Otherwise, very cool idea - just trying to figure out how you plan to overcome that.