Most beginners underestimate rental costs for the same reason: the expenses that hurt are the ones that do not show up on a monthly statement. This article lists the costs that are most often left out, shows how to turn them into a monthly number, and explains where our calculator fits them.
If your lender collects taxes and insurance through escrow, they are already inside your PITI payment, and you should not enter them again. If you pay them yourself, they must still be counted once. The most common beginner error is a mortgage figure that is principal and interest only. In the calculator, enter the full PITI in the mortgage field and use "other expenses" only for what is not already in it.
Routine repairs are small and frequent. Capital expenditures, or CapEx, are the large replacements: a roof, a heating and cooling system, a water heater, flooring. The way to see their monthly cost is to divide the price by the years you expect the item to last. These numbers are illustrative; get local quotes:
| Item | Assumed cost | Assumed life | Per month |
|---|---|---|---|
| Roof | $12,000 | 20 years | $50 |
| Heating and cooling | $7,500 | 15 years | $42 |
| Water heater | $1,200 | 12 years | $8 |
| Total set-aside | about $100 |
On a $2,000 rent, $100 is 5%. That is why a maintenance allowance of 5% to 10% of rent is a common starting point for investors, though your own number should depend on the age and condition of the building. In the calculator, raise the maintenance percentage to include CapEx, or add a fixed amount to "other expenses".
Between tenants you lose rent and usually pay for cleaning, small repairs, and advertising. Vacancy is not guaranteed in any particular year, but over many years it is a normal part of renting. IRS Publication 527 notes that you can generally deduct ordinary expenses of keeping a vacant rental in condition, but you cannot deduct the rent you did not receive. In other words, the lost rent is a real loss to you.
Management contracts often charge a percentage of collected rent, and some add leasing or renewal fees. Read the contract. Even if you plan to self-manage, a management line helps you compare the deal against what it would earn if someone else ran it.
Owners often pay water, trash, lawn care, snow removal, pest control, or common-area charges. Individually these are small. Together they can be a few hundred dollars a month. List them from the seller's records or from the utilities themselves, not from memory.
A purchase can change a property's tax assessment, and insurance premiums can rise. Rent does not always rise at the same speed. Re-run the numbers each year with current figures.
Some investors use an informal rule of thumb that operating expenses, not including the mortgage, will take roughly half of the rent. It is only a shortcut. It is not an official standard, and the real share varies by property type, age, location, and whether the owner pays utilities. Use it, if at all, as a sanity check against your itemized list, never as a replacement for it.
Take a unit that rents for $2,000. The mortgage (PITI) is $1,350. A first-time buyer who only subtracts the mortgage sees $650 of monthly cash flow. Now add 8% management ($160), 5% maintenance ($100), 5% vacancy ($100) and $90 of other costs. That is $450 of additional monthly costs, and the real estimate falls to $200. The $450 difference is the amount many new landlords find out about only after a bad month.
How much should I set aside? There is no official figure. Start with a percentage of rent you can defend, check it against the age of the systems, and review it after your first full year of actual bills.
Should reserves go in a separate account? Many landlords keep a dedicated account so that a large repair does not come out of their personal budget, but that is a personal choice, not a requirement.
Is every item above deductible? Tax treatment differs between repairs, improvements and depreciation. See our cash flow vs. profit article and IRS Publication 527, and ask a tax professional.