Numbers & Deals · Arthur the Developer · 17K views

My $403,000 Duplex - Construction Cost Breakdown

A real duplex build opened up line by line: land, construction, fees, and what was left as profit.

Real numbers from a real $403,000 duplex build, opened up line by line in the video. Here’s how to read a cost breakdown like a developer.

The cost stack

Every build reduces to three buckets: land, construction (including the builder’s fee), and transaction costs on exit. Profit is what the sale price leaves after all three. The discipline is deciding those numbers before you buy, not discovering them after.

Run your own numbers

The developer’s formula: sale price minus land, construction, and ~3% selling costs. Investment build assumes ~10% down + closing.

Target sale priceLand costConstruction + builder fee

$97,500

Est. profit

18%

ROI on cost

20%

Land % of sale

136%

Cash-on-cash

Rules of thumb from the BuildUp playbook: land at 20-25% of sale price or less, and a minimum 20% ROI (target 25%) before breaking ground. Red numbers mean the deal doesn’t pencil yet. Estimates only, not financial advice.

Why duplexes pencil

Two doors on one lot spreads the land cost across two units, and duplexes give you exit flexibility: sell both, rent both, or live in one and rent the other. Several of our community members chose a duplex as their first project for exactly that reason.

A duplex is often the smallest project with a built-in plan B. That flexibility is worth as much as the margin.

Ready to stop watching and start building?

Join the BuildUp Challenge and book a call with our team.

Join the BuildUp Challenge

Watch more on Arthur's channel.