The Breakdown Ford reportedly showed dealers a four-door Mustang prototype. Ford’s four-door Mustang has long been rumored, but the performance sedan is finally getting closer to becoming a reality. The automaker reportedly told dealers that the four-door Mustang will have a starting price of under $40,000. AN’s sources described the prototype as “boxy and wide,” although executives told dealers that the design has not been finalized. So, a four-door Mustang makes sense, not only from a cost perspective, but also a competitive one.