The three lines that are always real and never invoiced
Vacancy, routine maintenance and capital expenditure share one awkward property: in most individual months they cost nothing. A unit that is occupied has no vacancy cost this month. A month where nothing breaks has no repair cost. A roof with eight years left sends no bill. So a landlord looking at a bank statement in month four sees a surplus and concludes the property produces that surplus.
It does not. The vacancy arrives in a lump, usually three to six weeks of nothing plus a make-ready. The repairs arrive irregularly and average out over years rather than months. The roof arrives once, as a single number with four digits in it. Averaging them forward into a monthly figure is not conservatism, it is just correct accounting applied to costs that happen to be lumpy.
The test is simple. If a deal works only when these three lines are set to zero, it is not a deal that works. It is a deal that has not yet had a bad month.
How the capital reserve is built here
Each capital item gets its own line rather than being lumped into a single percentage, because the percentages people use come from portfolios and your property has specific parts with specific remaining lives. A roof that was replaced two years ago and a roof with three years left produce very different monthly numbers even though the property looks identical from the street.
The arithmetic per item is replacement cost divided by the months until it is due. A $12,000 roof twelve years out is $12,000 divided by 144 months, which is $83.33 a month. Add the furnace, the water heater, the interior turn and the appliances and the total is usually somewhere between $200 and $400 a month on an ordinary single-family rental — a figure that often exceeds the entire quoted cash flow.
| Item | Why the number moves |
|---|---|
| Roof | Material and pitch change the cost by a factor of two or more. Remaining life is the variable people guess worst. |
| Heating and cooling | Replacement is rarely just the unit. Ducting, electrical and permits ride along with it. |
| Water heater | Cheap to replace, short-lived, and the failure mode is water on a floor rather than a polite warning. |
| Flooring and repaint | Not a between-tenant touch-up. This is the full turn that happens every several tenants. |
| Appliances | They fail one at a time, which makes them feel like maintenance until three of them go in the same year. |
Remaining life is an estimate and it will be wrong. Being wrong by two years on the roof changes the monthly reserve by about fifteen dollars, which is survivable. Setting it to zero changes it by eighty-three, which is not.
Reserve against sinking fund against emergency fund
These are three different pots and mixing them causes the failure they were each supposed to prevent. The capital reserve here is a sinking fund: money accumulating toward a known future expense on a rough schedule. Routine maintenance is an operating expense that happens to be irregular. An emergency fund is separate again — it covers the thing you did not model, such as a tenant leaving four months early while the water heater fails.
If the same account holds all three, the first roof consumes the vacancy cover and the emergency cushion at the same time. Whether you keep them in separate accounts or in one account with a spreadsheet is a matter of temperament. Whether you count them separately is not.
What this page does not decide
It arranges the numbers you enter. It does not tell you whether the rent is achievable, whether the property will hold its value, or whether the deal is worth doing. It also stops well short of anything tax-related: depreciation, deductible expenses, how a capital improvement is treated against a repair, and what any of it does to your return are questions with answers that depend on federal rules, your state, the entity holding the property and your own situation, and they change. A CPA who does rental returns is the source for that, and the conversation is worth having before the first purchase rather than after the first tax year.
The same applies to what you can and cannot do as a landlord. Notice periods, deposit handling, entry rights, habitability standards and eviction process are state and often city law, they differ enormously, and getting them wrong is expensive in a way no reserve covers. Once the arithmetic here looks survivable, take the cap rate and NOI view for how the property compares to others, and the stress test for how far the rent can fall before this page turns red.
Questions people ask
Should the capital reserve be a percentage of rent instead?
A percentage is a shortcut and it is a reasonable one when you have no information — figures in the range of five to ten percent of rent get used for capital items, on top of a similar figure for routine maintenance. The problem is that it scales with rent rather than with the building, and a roof does not cost more because the rent went up. On a specific property you already know roughly what the roof costs and roughly how old it is, so the per-item calculation uses information the percentage throws away. Use the percentage for screening a listing in thirty seconds, and the item list once you have walked the property.
What if I do the repairs myself?
Then the labour half of each capital item is paid in your weekends rather than in dollars, and the materials half is still paid in dollars. Enter the materials cost plus whatever you would have to hire out, and be honest about which items you would genuinely take on. Roofing and heating work are not usually on that list, and in many places some of it requires a licensed trade regardless of your skill. What self-performing does not do is remove the cost — it converts it into unpaid time, which is worth accounting for even though the calculator cannot price it for you.
Is a landlord insurance policy different from my homeowner policy?
They are different products and a policy written for an owner-occupied home is generally not the right cover for a property you rent out. Beyond that, the specifics are between you and an insurer: what is covered, what loss of rent provisions exist, what your liability position is, and what any lender requires all vary by carrier, by state and by property. Tell your insurer plainly that the property is tenant-occupied before anything happens, rather than after. The number this page wants is simply the annual premium you are actually quoted.
The cash flow is negative. Does that mean it is a bad deal?
It means the property does not pay for itself out of rent under the numbers you entered, which is a fact rather than a verdict. Some people deliberately hold a property with negative cash flow because they expect other things from it, and the honest version of that position is knowing the monthly figure and having a reliable source for it through vacancies and repairs. This page does not judge the deal and neither should any calculator. What it can tell you is the size of the hole, which is the part that gets estimated optimistically otherwise. The total return page shows what else the property returns besides cash, and is careful about which parts of that you can spend.
Why is vacancy taken off before the management fee?
Because management fees are almost always charged on rent actually collected, not on rent scheduled. If the unit is empty, there is no rent and there is usually no percentage fee on it, though some agreements have minimums or separate leasing fees for finding the next tenant. The order matters more than it looks: taking eight percent off the scheduled rent rather than the collected rent overstates the fee by the vacancy rate. Check your own management agreement for how leasing and renewal fees are charged, since those are often flat amounts that this page does not model.