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The rent-regulation service

Shipped

What can this property legally charge?

A service answering a question with no clean data source anywhere, built at DoorFeed. Rent ceilings across French rent-control sectors and English affordable-rent schemes, with every figure traceable to the decree behind it.

  • Python
  • FastAPI
  • PostgreSQL
  • AWS
    First commit to the service answering live queries in production.
    days to production
    The problem

    Property investment analysis across the UK and France turns on one question: what rent is this unit legally allowed to charge. There is no clean feed for it. The answer lives in prefectural decrees, council mapping services and boundary sets, in a different shape in every jurisdiction, and getting it wrong means a valuation that is quietly illegal.

    The approach

    Build the service that answers it directly rather than leaving the rules in analysts' heads. Public decrees, council mapping services and boundary sets normalise into one dated lookup, and the valuation logic applies French rent control and English social and affordable rent rules per unit.

    The part that was actually hard

    Provenance, not volume. A number an institution cannot audit is a number it cannot act on, so every figure traces back to the specific decree that set it, and the lookup is dated because the rules change underneath you.

    Where it landed

    Empty repository to production in 27 days, sitting under the agent platform that turns it into analyst output. What can be said publicly stops at what it does; how it is built inside stays at work.

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