Build a custom commercial underwriting engine with Claude instead of buying Argus
Solo GP Jeremy Apfel, with about $500 million of industrial, office, and multifamily assets, built the underwriting platform Reversion Technologies largely himself with Claude, feeding the model graduate-level real estate material plus years of historical model inputs and outputs to build a deterministic cash flow engine over several thousand hours.
At a glance
- Tools used
- ClaudeClaude Code
- Category
- Investing & underwriting
- Audience
- investor
- Difficulty
- Builder
- Source
- How a CRE Investor Built an Argus Alternative With AI
PLOT Daily (AI for CRE Collective) · Article · Aug 7, 2026 - First step
- Gather 3 past deals where you know the correct cash flow outputs to use as test cases.
Suggested prompt
Written by this directory, inspired by the source. Replace the [bracketed] parts.
I want to build a deterministic lease-by-lease cash flow calculator. Here are 3 historical deals with inputs and the correct annual cash flow outputs: [attach]. 1. Write the calculation spec: base rent, escalations, free rent, recoveries with base-year stops, vacancy, and reversion. 2. Implement the spec in [Python/Excel formulas] and write a test that compares the outputs to my historical deals within $1. 3. Report every mismatch and the likely cause. Do not change my historical numbers to make tests pass.