Would you also ask why the insurance cost is a concern? That phrase may refer to an actual quote, a lender requirement, prior damage or merely an assumption. Each has a different place in the analysis.
For catchment data, I would not use one global field labelled simply “school area.” Keep the country or jurisdiction, the date the information applies to, and where the boundary information came from alongside the property record. Otherwise a clean-looking integration may present old or locally...
I would not treat that unexplained work as a minor detail. Ask what it covers, whether quotes exist, how the cost would be allocated and whether current reserves could cover any of it. Until those answers arrive, model a separate contingency rather than entering zero.
Also compare recurring...
Before adjusting for floor area, what does the 140 m² include? If one listing reports internal space while another includes circulation, storage or other areas, the apparent discount or premium may be meaningless. I’d also want to know whether the flat has parking or private outdoor space and...