Key Takeaways
- Apply category-specific growth rates to each expense line item—do not use a single blanket escalation rate.
- Exit cap rate has an outsized impact on IRR; add 25-50 basis points to the going-in cap as a conservative reversion premium.
- Stress-test vacancy, rent growth, interest rates, exit cap, and CapEx to find break-even points for each variable.
- Make acquisition decisions based on the conservative scenario—if it works there, base and optimistic cases provide upside.
A single-year pro forma captures current performance, but investment decisions require multi-year projections that model rent growth, expense escalation, capital expenditures, and exit assumptions. This lesson teaches you to build a five-year pro forma spreadsheet and then stress-test it by varying key assumptions to find break-even points and worst-case scenarios.
Constructing the Multi-Year Model
Start with your validated Year 1 pro forma as the foundation. For each subsequent year, apply growth assumptions to each line item. Revenue: apply market-based rent growth rates (typically 2-4% in normal markets; verify against historical submarket data and forward projections from CoStar or CBRE). Expenses: apply category-specific escalation rates—property taxes may increase 2-3% annually between reassessments, insurance has been escalating 5-10% in many markets post-2020, utilities grow at 3-5%, and management scales with revenue. Do not apply a single blanket growth rate to all expenses—each category has its own dynamics. Model capital expenditures (roof replacement, HVAC, parking lot) as lump-sum items in the years they are expected, funded from reserves or cash flow.
Modeling the Exit
The disposition (exit) assumption has an outsized impact on IRR and equity multiple. The standard approach is to apply an exit cap rate to the forward year's NOI (the year after you sell). Exit cap rate assumptions require careful judgment: if you are buying at a 7.0% cap rate, assuming an exit at 6.0% is speculative and aggressive (it assumes cap rate compression). A conservative approach adds 25-50 basis points to your going-in cap rate as a reversion premium (exit at 7.25-7.50%). The resulting sale price minus selling costs (broker commissions, transfer taxes, legal fees—typically 2-3% of sale price) minus remaining loan balance equals net sale proceeds to equity. Always run exit cap rate sensitivity to see how your IRR changes across a range of exit assumptions.
Stress-Testing Key Variables
Stress-testing identifies the break-even points where your investment thesis fails. Key variables to stress include: vacancy (what vacancy rate makes DSCR fall below 1.25x?), rent growth (what happens if rents are flat or decline 5%?), interest rate (if you have variable-rate debt, what rate breaks the deal?), exit cap rate (what exit cap makes IRR drop below your hurdle rate?), and capital expenditures (what if a major system fails in Year 2?). For each variable, find the break-even point and assess its probability. If the break-even vacancy rate is 12% and the submarket has never exceeded 9% even in recession, the deal has adequate safety margin. If break-even vacancy is 7% and the submarket averaged 6.5% last year, the margin is dangerously thin.
Guided Practice: Stress-Testing a 30-Unit Acquisition
You are underwriting a 30-unit property at $3.6M with NOI of $252,000 (7.0% cap), $2.88M loan at 6.75%, and $720,000 equity. The base case shows 18% IRR. You need to identify deal vulnerabilities.
- 1Calculate base DSCR: $252,000 NOI / $192,000 debt service = 1.31x. Adequate but not generous.
- 2Stress vacancy: at what vacancy rate does DSCR hit 1.0x? Solve: revenue decline of $60,000 (23.8% vacancy on $504,000 GPR). Break-even vacancy ≈ 24%—very safe.
- 3Stress rent growth: model 0% rent growth with 3% expense growth for 5 years. Year 5 NOI = $218,040 (NOI declines 13.5%). IRR drops to 11.2%—still above 10% hurdle.
- 4Stress exit cap: what exit cap makes IRR = 0%? At 10.5% exit cap, IRR ≈ 0%. At 9.0% exit cap, IRR ≈ 8%. Break-even exit cap of 10.5% is far above current market, providing comfort.
- 5Stress interest rate (if variable): at 8.5% rate, debt service rises to $228,000. DSCR = 1.11x—below lender minimum. This deal is vulnerable to rate increases.
- 6Conclusion: the deal is robust on vacancy, rent growth, and exit cap, but vulnerable to interest rate increases. Recommend fixed-rate financing or an interest rate cap.
Key Takeaways
- ✓Apply category-specific growth rates to each expense line item—do not use a single blanket escalation rate.
- ✓Exit cap rate has an outsized impact on IRR; add 25-50 basis points to the going-in cap as a conservative reversion premium.
- ✓Stress-test vacancy, rent growth, interest rates, exit cap, and CapEx to find break-even points for each variable.
- ✓Make acquisition decisions based on the conservative scenario—if it works there, base and optimistic cases provide upside.
Sources
- Argus Software — DCF Modeling Best Practices(2025-01-15)
- CBRE — Cap Rate Survey(2025-01-15)
Common Mistakes to Avoid
Using the same cap rate for entry and exit without any expansion buffer
Consequence: Assumes the market will be identical at disposition, ignoring cycle risk and property aging
Correction: Add 25-50 basis points to the going-in cap rate for the exit cap rate as a conservative buffer
Stress-testing only one variable at a time instead of combined scenarios
Consequence: Misses correlated risks where vacancy rises AND rent growth slows simultaneously during downturns
Correction: Run combined downside scenarios that stress multiple variables together, not just one in isolation
Test Your Knowledge
1.What is the purpose of stress-testing a pro forma?
2.In a multi-year pro forma, what is the exit cap rate used for?
3.Why should the exit cap rate be higher than the going-in cap rate?