Key Takeaways
- If the seller's OER is below 35%, expenses are almost certainly understated—investigate systematically.
- Post-sale tax reassessment is the most commonly missed adjustment and can reduce NOI by $5,000-$15,000+.
- Always impute management fees (8-10% of EGI) even for self-managed properties.
- Build a complete expense checklist and compare against the T-12—missing categories should be added at benchmark rates.
Sellers have strong incentives to understate operating expenses—every dollar of hidden expense inflates NOI by a dollar, potentially inflating the property's value by $14-$20 at typical cap rates. This lesson provides a systematic workflow for validating each expense category against benchmarks, identifying missing expenses, and adjusting for post-acquisition cost changes.
Expense Benchmarking by Category
Start by comparing total operating expenses to the NAA (National Apartment Association) or IREM (Institute of Real Estate Management) benchmarks for similar property types and geographies. Stabilized multifamily properties typically run 35-50% OER. If the seller's T-12 shows a 28% OER, expenses are almost certainly understated—either they are self-managing without imputing management fees, performing maintenance themselves, or omitting expense categories entirely. Walk through each category: property taxes (verify against county assessor, and model post-sale reassessment at purchase price), insurance (get an independent quote from your broker), repairs and maintenance (at least $500-$1,000 per unit per year for stabilized properties), management (8-10% of EGI even if self-managed), and utilities (verify against 12 months of actual bills).
| Expense Category | Benchmark Per Unit/Year | Common Seller Tactics |
|---|---|---|
| Property Taxes | $1,200-$3,000 | Not modeling reassessment on sale |
| Insurance | $400-$800 | Showing old policy before rate increases |
| Repairs & Maintenance | $500-$1,000 | Self-performing without accounting for labor |
| Management | 8-10% of EGI | Omitting because owner self-manages |
| Utilities | $600-$1,500 | Showing only common area, not owner-paid units |
| CapEx Reserves | $250-$500 | Omitting entirely (not an operating expense but critical for budgeting) |
Expense benchmarks per unit per year (national multifamily averages)
The Tax Reassessment Trap
Property tax reassessment on sale is one of the most commonly missed expense adjustments. In many jurisdictions (Florida, California under Prop 13 transfer, Michigan, and others), the assessed value resets to the purchase price upon sale. If a long-term owner has been paying taxes on a $1.2M assessed value and you buy for $2.0M, your taxes could increase by 60% or more. Always model post-acquisition taxes based on the purchase price multiplied by the local millage rate, not the seller's current tax bill. This single adjustment can reduce NOI by $5,000-$15,000 or more, fundamentally changing deal economics.
Identifying Missing Expenses
Common expenses that sellers omit or understate include: management fees (self-managed properties show no management expense—add 8-10% of EGI), CapEx reserves (not an operating expense but essential for budgeting—add $250-$500/unit/year), legal and eviction costs ($100-$300/unit/year for older Class C properties), turnover costs ($1,500-$3,000 per unit turn including cleaning, paint, carpet, and lost rent), and seasonal expenses that may not appear in the T-12 period (snow removal, annual HVAC servicing). Build a checklist of all standard expense categories and compare against the seller's T-12—any missing category should be added at benchmark rates.
| Expense Category | SFR Rental | Small Multi (2-4) | Mid Multi (5-50) | Large Multi (50+) |
|---|---|---|---|---|
| Property Taxes | 15-25% of EGI | 12-22% of EGI | 14-22% of EGI | 12-18% of EGI |
| Insurance | 4-8% of EGI | 3-6% of EGI | 3-5% of EGI | 2-4% of EGI |
| Maintenance & Repairs | 8-15% of EGI | 6-12% of EGI | 5-10% of EGI | 4-8% of EGI |
| Property Management | 8-12% of EGI | 7-10% of EGI | 5-8% of EGI | 3-6% of EGI |
| Utilities (Owner-Paid) | 0-5% of EGI | 3-8% of EGI | 5-12% of EGI | 4-10% of EGI |
| Capital Reserves | 3-5% of EGI | 3-5% of EGI | 2-5% of EGI | 2-4% of EGI |
| Administrative/Legal | 1-3% of EGI | 1-3% of EGI | 1-3% of EGI | 1-2% of EGI |
| **Total OpEx Ratio** | **39-73%** | **35-66%** | **35-65%** | **28-52%** |
Operating expense benchmarks by property type. Larger properties benefit from economies of scale. Source: IREM Income/Expense Analysis, NAA Operating Cost Survey, 2024.
Guided Practice: Rebuilding Expenses on a Self-Managed 12-Unit
A self-managing owner presents a T-12 showing $42,000 in total operating expenses on EGI of $156,000 (27% OER). You need to identify missing and understated expenses.
- 1Compare OER to benchmark: 27% is far below the 35-50% range, confirming expenses are understated.
- 2Property taxes: seller shows $14,000 on old assessment. At $1.4M purchase price and 1.8% effective rate = $25,200. Adjustment: +$11,200.
- 3Management: seller shows $0 (self-managed). Impute at 8% of EGI: $12,480. Adjustment: +$12,480.
- 4Insurance: seller shows $4,800. Your broker quotes $6,800 for comparable coverage. Adjustment: +$2,000.
- 5Repairs: seller shows $6,000 ($500/unit). Benchmark is $750/unit for 1978-built property. Adjustment: +$3,000.
- 6Missing categories: no legal/eviction budget, no pest control, no landscaping line item. Add $4,200. Adjusted total OpEx: $42,000 + $11,200 + $12,480 + $2,000 + $3,000 + $4,200 = $74,880. Adjusted OER: 48%. Adjusted NOI drops from $114,000 to $81,120—a 29% reduction.
Key Takeaways
- ✓If the seller's OER is below 35%, expenses are almost certainly understated—investigate systematically.
- ✓Post-sale tax reassessment is the most commonly missed adjustment and can reduce NOI by $5,000-$15,000+.
- ✓Always impute management fees (8-10% of EGI) even for self-managed properties.
- ✓Build a complete expense checklist and compare against the T-12—missing categories should be added at benchmark rates.
Sources
Common Mistakes to Avoid
Using the seller's current property tax bill without adjusting for reassessment
Consequence: Post-sale reassessment can increase taxes 20-50%, destroying projected cash flow and returns
Correction: Calculate post-sale taxes using the purchase price, local millage rates, and any applicable homestead or assessment caps
Accepting self-managed properties at face value without imputing a management fee
Consequence: Understates true operating cost; lenders require a management fee and the property must eventually be professionally managed
Correction: Always include 6-10% of EGI as a management fee, whether the property is self-managed or third-party managed
Test Your Knowledge
1.What is the single largest operating expense for most multifamily properties?
2.Why is tax reassessment risk critical in acquisition underwriting?
3.Which expense category is most commonly missing from seller-provided operating statements?