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Mobile Apps/Store-pending

Mieter App

German tenant-rights companion. 8-city Mietspiegel, Mietpreischeck, Nebenkostenprüfung, PDF export.

8
cities
98
tests
5
features
Live demo

Mietpreischeck — try it here

5-city preview

Simplified version of what the Mieter App does on a phone. The production app uses PLZ-level Mietspiegel tables per Bezirk; this preview uses one mid-range band per city.

Range for Berlin (10xxx, 12xxx, 13xxx): 7.50 – 12.80 €/m² · Mietspiegel Berlin 2025
Above range
15.08 €/m² is 17.8 % over the upper end (12.80 €/m²) for Berlin. That crosses the 10 % Mietpreisbremse threshold under §556d BGB. In the production app this is where the §557 BGB Widerspruchs-Vorlage opens automatically.

The problem

A Mieterbund membership costs ~€70 per year and still leaves tenants Googling §573c deadlines at 11 PM the night before they need to respond to a Kündigung. The legal data is public, the math is deterministic, and the offline case is the most common one. We built Mieter App because a tenant-rights calculator does not need a backend, a subscription, or a data broker.

How we built it

  1. 01MietspiegelRepository with curated JSON data for 8 cities, loaded locally, queried by Postleitzahl and Baujahrsklasse.
  2. 02Mietpreischeck flow that runs §556d BGB validation and auto-generates a PDF Rügeschreiben via share_plus — no print dialog, straight to WhatsApp or email.
  3. 03BetrKVRulesEngine: 22-category Nebenkosten classifier + six rule checks, fed by a dynamic entry UI and a Widerspruch-PDF generator.
  4. 04Seven Mieterrechte-Themen with four Musterbriefe (copy-to-clipboard) and a §573c BGB Kündigungsschutz calculator honoring the 3.-Werktag rule.

Outcome

Five phases shipped, 98 of 98 tests passing, zero analyzer warnings, SharedPreferences-based theme persistence, explicit Haftungsausschluss. Built end-to-end in a single focused development pass.

Stack

FlutterDartSQLiteshare_plus

Flutter + Dart. SQLite for local persistence. share_plus for PDF / text export. No backend, no accounts, no tracking.

Next up

Phase 4b OCR for scanned Nebenkostenabrechnungen, plus optional Phase 6 launch prep once store credentials swap.

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