A rental property is not attractive because the rent looks high, the purchase price looks low or the neighborhood is growing. A good investment is the result of several variables working together at the same time.
Start with income, but do not stop at gross rent
Gross scheduled rent is the top line. The investor must then account for vacancy and credit loss before estimating effective rental income. Additional income such as parking or utility reimbursements can be added where appropriate, but should be based on realistic operating history.
NOI is the property-level operating engine
Net operating income is generally calculated before mortgage payments and income taxes. It is the income left after normal property operating expenses such as taxes, insurance, repairs, management and other recurring costs.
This makes NOI useful for comparing properties with different financing structures. A property with weak NOI does not become economically strong merely because a buyer obtained an unusual loan.
Cap rate is useful—but incomplete
The capitalization rate is NOI divided by purchase price or value. It provides a quick measure of unlevered income yield. But it does not show the investor's actual cash return after financing, nor does it account for future capital expenditures, appreciation or tax effects.
Cash-on-cash return brings financing into the picture
Cash-on-cash return compares annual pre-tax cash flow to the actual cash invested. This can help evaluate leverage, but the number can be manipulated by using very high debt or by understating repairs and reserves. A high cash-on-cash return is not automatically a low-risk investment.
Market fundamentals determine whether today's numbers are durable
Property-level math should be tested against local fundamentals: employment, household growth, new construction, vacancy, rent growth, taxes, insurance and regulatory conditions. An excellent spreadsheet built on unrealistic future rents is still a poor underwriting model.
The bottom line
A good rental property is one that can survive ordinary surprises without requiring optimistic assumptions. The strongest acquisitions have enough income to cover realistic expenses, financing that does not overstrain cash flow, reserves for inevitable problems and a market that supports long-term demand.