How to estimate operating expenses
Operating expenses include taxes, insurance, maintenance, management, a CapEx reserve and a vacancy allowance. A common rule of thumb is the 50% rule: operating costs run near half of gross rent over the long run (often 35% to 50% for a clean single-family), before the mortgage.
The fastest way to turn a "good deal" into a money-loser is to forget costs. New investors subtract the mortgage from the rent, see a healthy number, and stop there. The buckets below are what quietly eat that number.
The cost buckets to include
- Property taxes and insurance. Usually your two largest items. Pull the real tax bill and get an actual insurance quote.
- Maintenance and repairs. A percentage of rent, never zero. Older homes cost more.
- Property management. Price it in even if you self-manage.
- Vacancy. No rental is occupied 100% of the time.
- Capital reserves (CapEx). Roofs, HVAC and water heaters wear out. Set money aside monthly.
- Utilities and other. Water, trash, lawn or snow, HOA, pest control, wherever they fall to the owner.
Rules of thumb when you lack real numbers
| Bucket | Ballpark |
|---|---|
| All operating expenses | 35% to 50% of gross rent (the 50% rule) |
| Maintenance | 5% to 10% of rent |
| CapEx reserve | 5% to 10% of rent |
| Vacancy | 5% to 8% of rent |
| Management | 8% to 10% of collected rent |
Worked example
On a home renting for $2,000 a month, a conservative estimate might be $250 taxes, $100 insurance, $150 maintenance, $150 CapEx, $120 vacancy and $200 management: about $970 a month, close to 49% of rent, before the mortgage.
What is NOT an operating expense
Your mortgage payment, depreciation and income taxes are not operating expenses; they sit below NOI. Capital improvements (a full renovation) are also treated separately from routine maintenance. That distinction is why cap rate and NOI deliberately exclude financing.
Frequently asked questions
What is the 50% rule?
The 50% rule is a screening heuristic: assume operating expenses (everything except the mortgage) will run about half of gross rent over the long run. It is a sanity check, not a substitute for line-by-line numbers.
What expenses count as operating expenses?
Taxes, insurance, maintenance and repairs, property management, utilities the owner covers, a vacancy allowance and a CapEx reserve. The mortgage, depreciation and income taxes do not count.
Should I include capital expenditures in operating expenses?
Big-ticket replacements (CapEx) are technically separate from operating expenses, but smart investors set aside a monthly CapEx reserve so the eventual roof or HVAC bill is not a crisis. Include that reserve in your underwriting.
How much should I budget for vacancy?
In a stable market, 5% to 8% of gross rent is typical, roughly a few weeks to a month of vacancy per year. Higher in soft markets or with frequent turnover.