The label that feels safe is often the one anchored to a market that no longer exists.
In 2021, underwriting 10% year one rent growth was called conservative.
Actual rent growth in many markets was running 20-30%. Anything below 10% was treated as leaving money on the table. A sponsor who modeled 8% would have lost the bid before best and final ever started.
That assumption worked. Until it did not.
And below I share the part many investors are still missing today.
The word was never describing the number
What looked conservative in 2021 was not actually conservative. It was a number anchored to a market environment that was already abnormal.
The cycle did not break the model. The model was already living inside a one in twenty year window and treating it as the new normal.
This is the trap. We tend to treat “conservative” as a property of the number itself. Ten is lower than twenty, so ten must be safe. But conservative is not a property of the number. It is a property of the relationship between the number and the conditions it depends on.
A low assumption resting on an unsustainable environment is not conservative. It is a smaller version of the same bet. When the environment normalizes, the smaller bet still loses, just more slowly.
That distinction is the whole game. An assumption is only conservative if it survives the conditions you cannot control. If it only survives the conditions you happen to be standing in, it is not protection. It is a borrowed sense of comfort.
The parallel is alive right now
3% is the new conservative.
It is the default in most Excel templates. It is what sponsors put in their decks without thinking twice. It sits in the rent growth cell the way ten percent once sat there, wearing the same costume of restraint.
But 3% is aggressive in a market with rent declines or heavy concessions or both. It is aggressive in a tertiary market whose long-term rent growth average is closer to 2%. It is aggressive any time the number cannot be defended with submarket data that is current and contextual.
The point is not that 3% is wrong. The point is that 3%, like 10% before it, is being treated as self-evidently safe when it is doing no such thing. It is a placeholder that has been promoted to a conviction without earning the promotion.
The discipline is not picking a lower number. The discipline is being able to defend the number you picked with evidence that holds outside the room you are sitting in.
Why this one input carries the whole structure
Rent growth is the top of the model. Every other number flows from it.
If the rent growth assumption is off, the year one cash flow is off. The year two net operating income is off. The refinance valuation is off, because it leans on that net operating income. The exit cap math is off, because it is applied to a stabilized number that never stabilized where the model said it would. And the limited partner distribution timeline is off, because distributions are the residual that arrives only after everything upstream behaves.
That is not a small modeling error. A two point miss at the top does not stay a two point miss. It compounds through every year and every dependent line until it reaches the one number you actually care about, which is when capital comes back to you and how much of it.
This is the part that does not show up in a glossy summary page. The summary shows a clean stack of returns. It does not show how violently that stack moves when the first input moves. A model is only as stable as its least defensible assumption, and the least defensible assumption is usually the one no one questioned because it looked modest.
The more useful question
For a limited partner reading a deck, the instinct is to ask whether the rent growth assumption is plausible. That is the wrong question, or at least an incomplete one. Plausible is a low bar, and plausibility is exactly what a well-built deck is designed to manufacture.
The more useful question is this. What does this deal look like at zero rent growth, and can the reserve and debt structure carry it for long enough to get to the other side?
Zero is not a forecast. It is a stress test. You are not predicting that rents will go flat. You are asking whether the deal survives if they do, because survival is the thing that determines whether you ever get to participate in the upside the deck is selling you.
If the answer is that the deal still services its debt, holds adequate reserves, and avoids a capital call at zero growth, then the rent growth assumption is a source of return rather than a source of solvency. That is where you want it. Return should depend on the assumption. The survival of your capital should not.
If the answer is that the deal only works because rents climb on schedule, then you are not underwriting a real estate investment. You are underwriting a forecast, and forecasts are the first thing a cycle takes away.
Closing thought
This is not only a rent growth lesson. It is a lesson about every input that wears a reassuring label.
The same trap lives in expense growth assumptions that look measured, exit caps that look prudent, and stabilization timelines that look reasonable, all anchored to conditions that may not hold. The word conservative is doing quiet work in each of those cells, and most of the time no one checks whether it has earned the title.
Discernment is not about finding more aggressive numbers to flag. It is about refusing to let a comfortable word or a model template stand in for evidence.
So here is the question worth carrying into the next deck that crosses your desk. When the deck says conservative, what is it actually describing: the discipline behind the number, or the market that happened to be standing behind it when the model was built?
Vessi Kapoulian
Breaking down multifamily underwriting one step at a time to create educated and empowered investors.
P.S. I have been working on something for investors who recognize this pattern. More soon.