Most people underwriting self-storage deals get lost in spreadsheets. In reality, only 5 numbers determine whether a deal works:

1. Economic occupancy (not physical) — physical occupancy lies. A facility at 92% physical occupancy with heavy discounting can perform worse than one at 85% at full rate.

2. Achievable rent vs. street rate — pull comps from 3-5 competitors within a 5-mile radius. If your in-place rents are more than 15% below street rate, you have a built-in value-add.

3. Expense ratio — self-storage typically runs 30-40% of revenue in expenses. Anything above 40% usually means deferred maintenance or a bloated management fee is coming.

4. Cap rate vs. debt cost spread — if your going-in cap rate isn't at least 150-200bps above your cost of debt, you're banking entirely on appreciation, not cash flow.

5. Cash-on-cash in year 1 — we don't touch a deal under 8% cash-on-cash in year one. If a deal only pencils on a 5-year IRR story, the underwriting is doing the selling, not the asset.

Run every deal through these 5 filters before you build the full pro forma. It'll save you hours on deals that were never going to work.

We built a full underwriting + automation + troubleshooting course around this framework — check the Vault Yield Academy page if you want the complete model and templates.