Only 6% of Code Carried Over When Team Built a Second Similar Product

A software team that built products for a rental company and a property developer found only 7 of 113 business concepts — roughly 6% — were shared between the two systems, despite the businesses appearing similar on the surface. Key differences such as construction-stage tracking, multi-month property transactions, and investor-only user roles meant most domain logic had to be rebuilt from scratch. However, the second product shipped significantly faster because foundational infrastructure — including logins, permissions, billing, messaging, and encryption — was reused wholesale from the first build. This shared layer, invisible to end users, accounted for roughly a third of the second product and required no rework. The team's core takeaway is that reusable infrastructure, not business logic, is where multi-product development pays off.