Interactive Calculator
Drag the sliders. The model recomputes instantly — monthly cash flow, the leverage test, and the exact down payment it takes to reach cost-neutral. Works on your phone.
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How to use it
Section titled “How to use it”- Start from a real deal. Punch in a price and gross rent from the Duck, Corolla, or Nags Head pages, then move the down-payment slider until the headline turns green.
- Watch the leverage line. When “unlevered yield” drops below “mortgage constant,” you’re in negative leverage — notice how raising the down payment (borrowing less) is the only lever that turns it green.
- Stress the cost stack. Push insurance from $12k → $18k (the coastal trajectory) and watch neutrality slip away. That’s the silent margin-killer from Insight #4.
- Find the break. The subtitle always tells you the exact down payment % for cost-neutral at your current inputs — that’s the number that actually matters.
Default assumptions (edit freely)
Section titled “Default assumptions (edit freely)”The sliders start on a representative $1.5M Duck-style oceanfront with a full cost stack: 18% management, 0.71% property tax, $12k insurance, and ~$23.5k of pool/utilities/maintenance/HOA. Rate defaults to 7.0% (July 2026). Everything is adjustable — the calculator makes no judgment, it just does the arithmetic honestly.