An understanding of fleet size and vertiport size sensitivity to demand and operational parameters is necessary to quantify the scalability of urban air mobility (UAM) services. In this work, we implement a bilevel rolling window fleet scheduling formulation that includes vertiport area as a secondary objective. We also present a simple vertiport area estimation methodology that leverages the fleet scheduling results and provides a lower bound on vertiport infrastructure area requirements. Lastly, we explore the sensitivity of fleet size and vertiport infrastructure requirements to several vehicle and operational parameters, including geographical demand distribution, daily passenger volume, vehicle passenger capacity, passenger aggregation window, battery charge rate, pad separation, and pad size. We find that, although the fleet size is reasonable for a UAM commuting service scaled to serve 10,000 passengers per day, vertiport area requirements are likely problematic under current sizing guidance from the Federal Aviation Administration, particularly area requirements for vertiports that serve as workplace hubs located in dense urban centers.