A collection of rentable units and associated structures in accordance with a particular embodiment of the present technology includes a first rentable unit encompassing at least a portion of a first retrofitted classroom within a retrofitted school building and a second rentable unit encompassing at least a portion of a second retrofitted classroom within the retrofitted school building. The first rentable unit includes a first reusable bathroom removably disposed in operable association with the first retrofitted classroom. Similarly, the second rentable unit includes a second reusable bathroom removably disposed in operable association with the second retrofitted classroom. The collection further comprises above-floor plumbing drain lines through which the reusable bathrooms are operably connected to a below-floor plumbing drain trunk line of the retrofitted school building.