How a PhD Underwrites Apartments: Jason Williams of Ironclad Underwriting

Jason Williams spent 15 years as a chemical engineer. He's owned real estate since 2003 and large multifamily since 2017. When he started underwriting apartments, half the spreadsheets he was handed had broken cells and equations that didn't work, so he built his own model. People kept asking him to show them how it worked, and that model became Ironclad Underwriting.

His rule is simple: never underwrite off your own numbers. The property manager tells him what each unit can rent for. The insurance broker prices the premium off comparable properties, and he uses the high end of the range. A tax advisor fights the assessment. And the plumber's bid gets multiplied by three, sometimes four.

"Every single property I've had from a 1950s build up to early 2000s has had major plumbing issues."

What Ed and Jason get into:

• Why a T12 almost never ties to the bank statements, and when that gap is actually a red flag
• Rent rolls that look clean but hide a rollover cliff, and why the manager, not the spreadsheet, sets pro forma rents
• Insurance priced on replacement cost, and what Texas nondisclosure does to your tax bill after you buy
• The tax advisor who saved him $20,000 one year and $11,000 this year, paid only on a percentage of what he saves
• Why he no longer chases agency debt, even with the better rates
• A 72-unit plumbing job that put residents in a hotel for two weeks, and a gas leak that shut off the gas over Easter weekend
• Ed's sewer line on a 10-unit building that passed inspection: a $5,000 to $10,000 fix at purchase that became $44,000 a year and a half later
• Six months of reserves, and why Ed doubled his after the pandemic
• The zoning mistake on a mobile home community that has cost Jason more than a year of unexpected debt service

Also in this episode, Questions from the Underground. An experienced Connecticut investor asked Ed whether it's time to cycle back to cash flow deals or keep riding the appreciation wave. Ed's answer: it's always a cash flow play. Appreciation is the cherry on top, not the basis of a business plan.

Books mentioned:

• Who Not How by Dan Sullivan with Dr. Benjamin Hardy, Jason's favorite
• The E-Myth Revisited by Michael E. Gerber

Connect with Jason Williams at ironcladunderwriting.com, or on LinkedIn. His free underwriting resources and his weekly underwriting podcast are on the site.

Got a question you want answered on the show? Send it to ed@clarkst.com.

Recorded September 2026.

Real Estate Underground with Ed Mathews. Find us wherever you get your podcasts, at clarkst.com/podcast or elevista.com/podcast

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