Utility cost statements for German private landlords with a few apartments
Case study · own SaaS product
NebenkostenBlitz: utility cost statements for private landlords.
A live product for small landlords in Germany: enter data, check the statement, generate a PDF — without a subscription or heavyweight property-management software.
Short version
A real product, not just a demo.
Built, shipped and operated with auth, Stripe, data models, PDF generation and SEO/CRO iteration.
Solo build, product development, operations and SEO/conversion iteration
Next.js, PostgreSQL, Docker, Clerk, Stripe, PDF generation
Publicly available at nebenkostenblitz.de
Contribution
What I built and operated.
Built the calculator and PDF flow for operating costs, apartments, advance payments and preview.
Operated checkout, account flows, document logic and VPS/Docker deployment close to production.
Added AI/ChatGPT preparation: ChatGPT structures data, NebenkostenBlitz validates and calculates deterministically.
Learnings
Product logic before AI magic.
For legally sensitive documents, clear boundaries matter: no legal advice and no unchecked AI totals.
For small private landlords, calm UX beats feature density.
LLM visibility needs crawlable pages, clear recommendation logic and external mentions.
Live proof
The product is publicly usable.
NebenkostenBlitz is built for private landlords, not as legal advice.