Conch House. Porch in front and back, overhanging roof to block the sun, and a hallway from front to back on one side to get to the one or two bedrooms. They are not large, and typically are made of pine. I tend to feel like a bull in a china shop in one of those buildings. They're built to withstand storms and allow the breezes to pass through. When you build them within inches of each other and plant them as thickly as this, I can't see much breeze getting through.
I can hear my Mom's voice in my head saying they are not something a family would live in but they are "quaint". Besides something with 3 bedrooms in the right part of Old Town Key West would be going for $500K and it would be small, under 1200 square feet. These little places are really an out building on an estate in size anywhere else and you are looking at almost the entire street frontage in the picture.