A high rental yield can hide weak cash flow. These seven checks turn a promising listing into a deal you can actually compare.
Research date: 26 September 2026. Figures in the example are hypothetical and pre-tax.
A hypothetical listing costs €180,000 and could rent for €1,250 a month. The gross rental yield is 8.3%. That sounds like the answer.
It is only the opening line. Add €20,000 of buying costs, repairs and furniture. Allow for an empty month now and then. Pay the building charges, insurance, maintenance and management. Add a mortgage. The same apartment now produces a 5.6% net operating yield, about €337 of monthly cash flow and a 4.4% cash-on-cash return.
In a mild downside case, that monthly cash flow falls to about €62. The apartment has not changed. The arithmetic has.
That is why one headline yield is not enough. The boiler does not accept gross yield as payment.
IN BRIEF
- Start with the total cash required, not the advertised purchase price.
- Check rent, vacancy and operating costs separately. Each estimate can be wrong in a different way.
- Use net yield to judge the property and cash flow to judge the financing.
- Calculate cash-on-cash return twice: once for the expected case and once for a realistic downside case.
The Seven Numbers at a Glance
The table follows one clearly labelled hypothetical long-term rental. It is a worked example, not a market forecast.
| No. | Number | How to calculate it | Example |
|---|---|---|---|
| 1 | Total cost and cash required | Purchase, buying costs, works, furniture and deposit | €200,000 all-in; €92,000 cash |
| 2 | Gross rental yield | Annual base rent / purchase price | 8.3% |
| 3 | Vacancy allowance | Uncollected rent / potential rent | 5% |
| 4 | Annual operating costs | Owner-paid recurring costs and reserves | €3,000 |
| 5 | Net operating yield | Net operating income / all-in property cost | 5.6% |
| 6 | Monthly cash flow | Net operating income less debt service | €337 |
| 7 | Cash-on-cash return | Annual pre-tax cash flow / cash invested | 4.4% |
1. Total Cost and Cash Required
The purchase price is not the price of entering the investment. Add transfer tax or stamp duty, legal and registration fees, financing costs, renovation, furniture and any required parking or storage space.
The OECD review of housing taxation notes that transaction taxes are common across OECD countries and can increase the buyer’s purchase cost. The rate and treatment vary by country, so use the local rule that applies to this property.
In the example, €180,000 becomes €200,000 after €12,000 of acquisition costs and €8,000 of repairs and furniture. With a €108,000 mortgage, the investor still needs €92,000 in cash.
For a wider cost framework, read The Hidden Costs of Buying Property in Europe.
2. Gross Rental Yield
Gross rental yield = annual base rent / purchase price × 100.
€15,000 / €180,000 = 8.3%.
Use the rent supported by current comparable leases, not the highest asking rent you can find. Gross yield is useful for quick screening. It ignores vacancy, running costs and debt.
For the full distinction, see Gross vs Net Rental Yield: What Investors Often Miss.
3. Vacancy Allowance
A flat does not need to be empty for a full year to damage the result. Tenant changes, repairs and slower leasing periods can remove weeks of income.
A 5% vacancy allowance reduces €15,000 of potential rent to €14,250 of expected collected rent. Use local evidence. A student property with a shorter letting term needs different assumptions from a stable long-term tenancy.
RICS guidance for buy-to-let valuation notes that letting periods, voids and the quality of rental evidence can affect the analysis.
4. Annual Operating Costs
Count the costs the owner pays even when the mortgage does not exist. Typical items include property tax, insurance, non-recoverable building charges, management, maintenance, landlord-paid utilities and a reserve for replacements.
Keep mortgage payments outside operating costs. This lets you compare the property first and the financing second.
| Income bridge | Annual amount | Meaning |
|---|---|---|
| Potential annual rent | €15,000 | 12 months at €1,250 |
| Vacancy allowance | -€750 | 5% of potential rent |
| Expected collected rent | €14,250 | Income after vacancy |
| Operating costs | -€3,000 | Owner-paid costs and reserves |
| Net operating income | €11,250 | Before mortgage and income tax |
5. Net Operating Yield
Net operating yield = net operating income / all-in property cost × 100.
€11,250 / €200,000 = 5.6%.
This is usually a better property-level comparison than gross yield. RICS notes that a net yield approach can provide a more accurate assessment for more complex or individual properties because relevant landlord expenditure can be included.
State your denominator clearly. Dividing by the purchase price will produce a higher yield than dividing by the full amount invested in the property.
6. Monthly Cash Flow After Debt
Annual cash flow = net operating income – annual debt service.
The example uses a €108,000 repayment mortgage at 4.5% for 25 years. The calculated payment is about €600 a month, or €7,204 a year.
€11,250 – €7,204 = €4,046 a year, or about €337 a month.
Use an actual lender quote, including mandatory fees and insurance. For a floating-rate loan, rerun the calculation at a higher rate. Positive cash flow with no safety margin can disappear after one repair or one empty month.
Compare the financing separately with Buying Property With Cash or a Mortgage?
7. Cash-on-Cash Return
Cash-on-cash return = annual pre-tax cash flow / cash invested × 100.
€4,046 / €92,000 = 4.4%.
This shows what the property produces from the cash you actually tied up. It is not total return. It excludes future price changes, mortgage principal repaid, tax and selling costs.
OECD research on effective housing taxation shows why the tax result cannot be reduced to one universal assumption. It changes with the holding period, tenure, financing, return and inflation. Calculate tax separately for the investor and country involved.
Run the Numbers Again When the Story Gets Worse
A base case tells you what may happen if the assumptions behave. A downside case shows whether the investment can absorb ordinary disappointment.
In the second version below, market rent is 10% lower, vacancy rises to 10% and annual operating costs rise to €4,200. The loan does not become friendlier just because the spreadsheet is having a bad day.
| Metric | Base case | Downside case |
|---|---|---|
| Potential annual rent | €15,000 | €13,500 |
| Vacancy allowance | 5% | 10% |
| Expected collected rent | €14,250 | €12,150 |
| Operating costs | €3,000 | €4,200 |
| Net operating yield | 5.6% | 4.0% |
| Monthly cash flow | €337 | €62 |
| Cash-on-cash return | 4.4% | 0.8% |
The Seven Numbers Tell One Story
The 8.3% gross yield was correct. It was also incomplete. After realistic buying costs and operating expenses, the property-level yield was 5.6%. After financing, the investor received a 4.4% pre-tax cash return in the base case. A modest downside reduced that return to 0.8%.
That does not automatically make the property good or bad. It tells you what must be true for the deal to work, how much cash it may produce and how thin the safety margin is. Those are the numbers worth checking before the viewing becomes an emotional commitment.
Use the same framework when comparing European property markets.
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This article is for general educational purposes. It is not personalised financial, tax or legal advice.