It is tempting to judge a rental cottage with simple math. Rent comes in, the loan payment goes out and the rest looks like profit. In practice, DADU rental expenses go well beyond the mortgage. Repairs, insurance, taxes, empty months and compliance all take a share of the rent.

This guide walks through the costs landlords commonly face and explains why reserves matter. It does not forecast prices or property values. Instead, it helps you build a fuller budget before you decide.

Why the Mortgage Is Only the Start

A loan payment is the most visible monthly cost, so it often gets the most attention. However, it is only one line in a longer list. Other costs arrive at random, such as a broken appliance or a leak after a storm.

Because of that, a budget that covers only the loan can fall short quickly. A complete plan lists every regular cost and sets aside money for the irregular ones. Then the rent can do its job without stress every time something breaks.

Repairs and Routine Maintenance

Every home needs upkeep, and a rental sees more wear than most. Gutters need cleaning, filters need changing and paint wears out. Also, appliances, faucets and door hardware eventually fail.

Some owners handle small jobs themselves, while others hire help for everything. Either way, time and money both count. Our post on DADU water heaters shows how equipment choices affect long term service needs.

A simple maintenance calendar helps. For example, plan gutter cleaning in fall, a heat pump service each year and a check of caulk and seals in wet areas. Regular care often costs less than emergency repairs. It also gives you a chance to spot small problems before they grow.

Building Reserves for DADU Rental Expenses

Large repairs do not arrive on a schedule. A roof, a heat pump or a water heater can need replacement in the same year as a vacancy. Therefore, many landlords set aside part of each month’s rent in a separate reserve account.

The right amount depends on the age and quality of the building, so a new cottage may need less at first. Still, reserves for DADU rental expenses should grow over time as systems age. Our guide to a DADU contingency budget explains a similar idea for the construction phase.

Insurance and Property Taxes

Adding a rental unit can change your insurance needs. A standard homeowners policy may not cover a tenant’s unit, so you may need a landlord policy or an endorsement. Liability coverage matters as well.

Ask a licensed agent to review your plans before the first lease. It also helps to ask whether the policy covers lost rent if damage makes the unit unlivable for a time.

Property taxes are another ongoing cost. In general, new construction can raise a property’s assessed value, which can change the tax bill. Because local rates and assessments vary, check with the county assessor rather than relying on general rules.

Vacancy and Turnover Costs

Even good rentals sit empty sometimes. Between tenants, you still pay insurance, taxes, utilities and any loan payment. In addition, turnover brings cleaning, touch up painting and advertising.

Screening applicants also takes time, especially if you check references and rental history carefully. As a result, a realistic budget assumes some empty weeks each year. It also includes the cost of getting the unit ready for the next tenant.

Utilities and Management

If you include utilities in rent, those bills are your cost. Even when tenants pay some services, owners often keep water, sewer and garbage. Our post on DADU separate meters explains how metering affects who pays.

Management is another choice with a price. A property manager can handle showings, leases, rent collection and repairs for a fee. Meanwhile, self management saves that fee but costs time. Either way, it belongs in the budget.

Smaller costs add up as well. Lawn care, snow and leaf cleanup, pest control and lock changes between tenants all appear on many landlord budgets. Likewise, advertising and tenant screening services carry their own charges.

Compliance Costs for DADU Rental Expenses

Rental rules bring their own costs. Seattle requires most rental properties to register with its rental registration and inspection program. The city’s RRIO page for owners and managers lists registration fees, renewal steps and inspection requirements. So include registration, renewals and any inspection costs in your list of DADU rental expenses.

Other compliance items may apply too, such as required notices, business taxes and record keeping. Because rules change, review city pages each year. A tax adviser can also explain how rental income and expenses affect your return.

Testing DADU Rental Expenses With Scenarios

Rather than one forecast, start with a few scenarios that use a cautious rent, every regular expense and a reserve. Then test a bad year with a long vacancy and a major repair. If the numbers still work, the plan has some resilience. If they do not, adjust the design, the budget or the rent before you build.

Avoid counting on rising property values to make the numbers work. Appreciation is uncertain, and it does not pay monthly bills. Focus instead on whether the rent covers costs today. If it does, any future gain in value is a bonus rather than a requirement.

In the end, a clear budget makes better decisions possible. Listing every cost helps you set rent, plan reserves and judge whether a rental fits your goals.