Why do Sullivan's Island homes need different valuation approaches?

Sullivan's Island needs a different valuation approach than a typical mainland neighborhood because flood zone, elevation certificates, short-term rental rules and proximity to the ocean all move price independently of square footage in ways an inland comp set never has to account for. A blended citywide average simply cannot capture that spread. Brian Beatty builds each Sullivan's Island valuation from island-specific comparable sales rather than a generic Charleston-area model.