These are not beginner mistakes. The errors below are made by experienced investors and operators who know the fundamentals of CRE underwriting but cut corners in their pro forma analysis. They cost real money because they create false confidence in deals that do not perform as projected.
After underwriting billions in real estate assets and reviewing hundreds of client models, these are the five most common mistakes I see in pro formas from experienced investors.
1. Projecting Rent Growth That the Market Cannot Support
The most common pro forma mistake is baking in annual rent growth that does not reflect the local market. A 3% annual rent growth assumption may sound conservative, but in a submarket where rents have been flat or declining for the past two years, 3% is aggressive.
Rent growth assumptions should be grounded in actual market data: trailing rent growth in the submarket, current supply pipeline, absorption trends, and local economic conditions. If new supply is flooding the market and vacancy is rising, projecting above-average rent growth is wishful thinking.
The danger is compounding. A 1% overestimate in annual rent growth does not just affect Year 1. It compounds across every year of the hold period. By Year 5, the projected NOI can be 5 to 8% higher than reality. By Year 10, the gap is even wider. This inflated NOI flows through to inflated valuations, inflated returns, and inflated confidence.
The fix is simple. Use market data to support your rent growth assumption. If you cannot find data that supports 3%, use 2%. If you cannot find data that supports 2%, use 1%. Let the deal work at conservative assumptions or do not do the deal.
2. Ignoring or Underestimating Capital Reserves
Many experienced investors treat capital reserves as an afterthought. They budget $200 or $300 per unit for replacement reserves and move on. In reality, deferred maintenance, roof replacements, HVAC systems, parking lots, and building systems require significantly more capital than most pro formas account for.
The problem is amplified in value add deals where investors are focused on the renovation budget but ignore the ongoing capital needs of the existing building systems. You may budget $15K per unit for interior renovations, but if the roof needs replacement in Year 3, that is $200K or more that was never in the model.
A proper pro forma should include both a replacement reserve line in the operating budget (for routine capital needs) and a separate capital expenditure schedule for known or anticipated major items. If the property has a 20-year-old roof, budget for the replacement. If the boiler is original, budget for the replacement. If you do not know the condition of the major building systems, that is a due diligence gap, not a reason to assume zero capital needs.
3. Trusting the Seller's Pro Forma
Every seller wants to maximize the perceived value of their property. Seller pro formas are marketing documents, not underwriting documents. They are designed to present the asset in the best possible light, and they do it in subtle ways that are easy to miss.
Common tactics include using "potential" rents instead of actual in-place rents, excluding non-recurring expenses that are actually recurring, including income from sources that are not guaranteed to continue, and applying expense ratios from a different market or property class. Some seller pro formas project performance that the property has never achieved and likely never will.
The fix is to rebuild the pro forma from actual operating data. Get the T-12 (trailing 12 months of operating statements), the actual rent roll, and the actual tax bills. Build the NOI from these documents, not from the seller's marketing package. If the seller's pro forma shows a significantly higher NOI than what the T-12 supports, that gap needs to be explained and verified before you underwrite to it.
4. Running a Single Scenario
A single scenario pro forma is a bet, not an analysis. It tells you what happens if everything goes according to plan. It does not tell you what happens if it does not.
Every pro forma should include at minimum three scenarios: a base case using conservative assumptions, an upside case reflecting the business plan working as intended, and a downside case testing what happens when key assumptions underperform. Beyond that, sensitivity analysis should show how returns change when you adjust rent growth, vacancy, exit cap rate, and expense growth individually.
Single scenario analysis is how investors convince themselves to do deals that should not get done. The base case looks great, so they move forward. Then rents grow at 1% instead of 3%, or vacancy runs at 8% instead of 5%, or the exit cap rate is 50 basis points wider than projected. Any one of these variances can materially impact returns. The combination of two or more can turn a projected home run into a loss.
Running multiple scenarios does not mean being pessimistic. It means understanding the range of outcomes so you can make a decision with full visibility into the risk.
5. Misaligning Assumptions Across the Model
This is the most subtle mistake and the one I see most often in models built by experienced investors. The individual assumptions in the pro forma may each be reasonable in isolation, but they are inconsistent with each other when taken together.
For example: projecting 4% annual rent growth while simultaneously projecting 3% vacancy. If you are growing rents aggressively, you will likely experience some occupancy pressure as tenants shop alternatives. Conversely, projecting flat rents with declining vacancy assumes increasing demand without any pricing power, which is rarely how markets behave.
Another common misalignment is projecting value add rent premiums without accounting for the vacancy loss during renovation. If you are turning 40 units over the course of a year, those units are offline during renovation. The pro forma needs to reflect that lost income, not just the higher rents after the turn.
The fix is to review the pro forma holistically. Do the assumptions tell a consistent story? Does the revenue trajectory align with the expense trajectory? Does the capital plan align with the projected lease up? Every assumption should be evaluated not just on its own merit, but in the context of all the other assumptions in the model.
The Bottom Line
Pro forma quality determines investment quality. A model built on aggressive, inconsistent, or unsupported assumptions creates false confidence that leads to real losses. The best investors build their pro formas with the same rigor they apply to every other part of their due diligence.
If you want an independent review of your underwriting or need a custom pro forma built from actual operating data, schedule a consultation. We build models that hold up under scrutiny.