Buy Box

Deal

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Net cash flow · year 1

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Screening

Stress test

Where the deal breaks, and the price that makes it work.

Custom scenario

Model your own bad year.

Interest rate

Rent

Months empty a year

Levy & rates

Income vs expenses · 20 years

Rent collected against running costs and the bond, each year

Rent covers all costs

Cash you top up

20-year net cash

Present value of that cash Discount rate %

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Projection

Net position if sold each year, today vs the perfect storm

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All deals

Click a row to open it. Click a column heading to sort.

Deals in this comparison

Up to 8. Colours stay with each deal.

Side by side

Best in each row is marked

Monthly cash flow

Bar: today · thin line: perfect storm

Net position if sold

By year of sale

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Market

New deals start at the prime rate. Saved deals keep their own rate

Prime lending rate

%

The default is 10.75%, last checked 28 September 2026. Update it when the Reserve Bank changes the repo rate. While the present-value discount rate equals prime, it moves with it.

Your buy box

The targets every deal is graded against. The defaults are common rules of thumb. Set your own.

Your data

Back up your deals or move them to another device

Export saves every deal and your targets as a JSON file. Importing adds the deals in a file to yours, replaces any deal with the same id and takes the targets from the file.

Method

How every number is worked out

GradeA to E

Each deal is scored on ten tests against your buy box. A test met counts 1, a test within reach counts ½. A = 90%+, B = 75%+, C = 55%+, D = 35%+, E below that. A and B fit your buy box.

1% ruleQuick screen

Monthly rent ÷ price. A 10-second first screen. At South African interest rates few apartments reach 1%, so anything near it is strong.

50% ruleQuick screen

Running costs usually take about half the rent. The expense ratio shows your own estimate. Far below 50%? Check for missing costs.

Cash flow, cap rate, DSCRQuick screen

NOI is rent collected less running costs. Cap rate is NOI ÷ price. Cash flow is NOI − bond payments. DSCR is NOI ÷ bond payments; lenders like 1.2 or more.

Gross and effective yieldYield & return

Gross yield is annual rent ÷ price. Effective yield is NOI ÷ total cost, including transfer duty, fees and upfront repairs.

Cash-on-cash (ROI)Yield & return

Annual cash flow ÷ cash you put in: deposit, transfer duty, attorney and bond fees, repairs. The default target is 12%.

Buying below valueYield & return

(market value − price) ÷ market value. Much of a property's return can be made on the way in: buying from a motivated seller, or fixing up an under-rented property.

Annualised returnYield & return

IRR over your hold: rent growth, cost growth, bond paydown, capital growth and selling costs.

Stress test

Each scenario reruns the full model with one input made worse. Breaking points solve for the exact rate, rent or vacancy where cash flow hits zero. Offer prices solve for the highest price that still meets your target, with duty and fees recalculated; levies and rates are held fixed.

Income vs expenses

Twenty years of rent collected (after vacancy) against running costs and bond repayments, using your rent and levy growth rates. The bond disappears once it's paid off. "Cash you top up" adds up every year the rent falls short. The sale of the property is left out.

Present value

Each year's net cash from the 20-year view, discounted back to today: Σ net ÷ (1 + rate)^year, with cash treated as arriving at each year end. The default rate is prime (set under Market), the return you'd get by paying down debt instead. Use your own required return if it's higher.

Tax

Add your marginal rate on a deal to see after-tax cash flow. Taxable rental income is NOI less bond interest; a loss usually reduces tax on other income. Grades use pre-tax numbers.

Before you offerChecklist

TPN report on tenant payment behaviour in the area
Levy statement and any planned special levies
Municipal account arrears
Title deed and approved building plans
Current tenant's status and arrears

Model checks

The engine is tested against an independent month-by-month bond simulation, the SARS transfer duty table, hand-built cash flows, and thousands of random and junk deals for consistency.

Transfer duty uses the SARS table effective 1 April 2025, unchanged for 2026/27 (last checked 28 September 2026). On new developments the developer usually pays duty and fees. Attorney and bond fees are estimates; get a quote. A calculator, not financial advice.

What the grade means

A quick screen, not a verdict on the property

Every deal gets a grade from A to E. It shows how well the deal meets your buy box: ten targets for cash flow, yield and return. Change a target and every grade updates.

Each test that is met scores 1 point. A test that is close scores half a point: within 20% of the target (15% for the expense ratio, where lower is better), or within R1,000 a month for cash flow. A test that can't be worked out is left out. For example, "below market value" needs a market value. The grade is the share of points scored.

A90% or more. Fits your buy box

B75% or more. Fits your buy box

C55% or more

D35% or more

EBelow 35%

The ten tests

With your current targets

The quick screens are fast first checks that many rental investors use. The yield and return tests look at what the deal earns on the money you put in. The default targets are common rules of thumb, not recommendations. Set your own in Buy box & method.

What the grade leaves out

The grade uses first-year, pre-tax numbers and only what you enter. It can't see the building's condition, the area, the tenant, the body corporate's finances or your own circumstances. A good grade means a deal is worth a closer look, not that you should buy it. The stress test and 20-year view show how a deal holds up when things go wrong. The checklist under Before you offer lists what to check next.

Not financial advice

Buy Box is a free calculator for learning and for screening deals. It is not financial, tax, legal or investment advice, and it does not recommend any property, bond or product. It is not provided by an authorised financial services provider.

The results are only as good as the numbers you enter. Rates, rents, costs, transfer duty and fees change, and the estimates may be wrong or out of date. Before you buy, speak to qualified professionals, such as a financial adviser, a bond originator, a conveyancing attorney and a tax practitioner.

Buy Box is provided as is, without any warranty. You use it at your own risk.

Before you make an offer. The free 10 checks before you sign one-pager lists what to look into, and which part of Buy Box does the maths for each.

Tell us what to fix. Something confusing, wrong or missing? Send feedback. It goes straight to the person who builds Buy Box.

Your privacy. Your deals are saved only in this browser and are never sent to us or anyone else. Clearing your browser data deletes them, so export a backup under Your data. Read the full terms of use and privacy notice.

Print it, or choose Save as PDF in the print screen, to keep a copy. Checks 1 to 8 link to the part of Buy Box that does the maths.

Buy BoxFree checklistbuyboxsa.co.za

10 checks before you sign an offer to purchase on a rental

An offer to purchase is binding once both sides sign it. These ten checks take an evening, and Buy Box does the maths for the first eight.

The cash flow after every cost
Rent minus the bond isn't the answer. Take off the levy, rates, insurance, management (about 10% plus VAT) and maintenance too.
In Buy Box: the monthly cash flow on Analyse
Rent that has actually been achieved
Compare at least three similar units that let recently, not asking rents. Ask a local rental agent what they would list it for.
In Buy Box: monthly rent, in the Quick form
The levy and the scheme's health
Ask for the levy statement, the body corporate's financial statements and reserve fund, and whether a special levy is planned.
In Buy Box: stress test, levy and rates up 25%
Rates and taxes
Check the municipal valuation and the current rate. A new valuation roll can push rates up.
In Buy Box: rates and taxes, in the Quick form
All the cash you need on day one
Deposit, transfer duty, attorney and bond fees, and repairs. A new development sold with VAT included usually has no transfer duty.
In Buy Box: cash required, on Analyse
Prime up 2%
The prime rate has moved by 2% or more within a few years before. Know your monthly number if it does again.
In Buy Box: stress test, prime up 2%
Two empty months
Tenants leave, and finding the next one takes time. Check the cash flow with two months empty a year.
In Buy Box: stress test, empty 2 months
The price that makes it work
Know the price at which it breaks even, and the price that meets your return target, before you make an offer.
In Buy Box: stress test, where it breaks
Condition and certificates
Have it inspected. On a resale the seller usually supplies an electrical compliance certificate, plus others where they apply. New homes should be NHBRC-enrolled.
Ask the agent and your attorney
The conditions in the offer
Make it subject to bond approval, with clear dates. Read the voetstoots clause, and have a conveyancing attorney look before you sign.
Share the investor report with your attorney

Prepared by

Prepared for

In the print screen, choose Save as PDF as the printer to keep a copy or send it on. The report is built in your browser; nothing is uploaded.

Terms of use

Last updated 3 October 2026

What Buy Box is. Buy Box is a free online calculator for screening South African rental property deals. It is run by an individual in South Africa. By using it, you agree to these terms. If you don't agree, please don't use it.

Not advice. Buy Box gives general information only. It is not financial, investment, tax or legal advice, and it does not recommend any property, bond, developer or product. It is not provided by an authorised financial services provider. Grades and results depend only on the numbers you enter and the targets you choose.

Estimates can be wrong. Interest rates, transfer duty, fees, rents and costs change. The built-in figures (the prime rate and the SARS transfer duty table) show when they were last checked, and they may be out of date. The example deals are made up and are not real listings. Check every number yourself.

Your decisions are your own. Before you buy, sell or borrow, get advice from qualified professionals, such as a financial adviser, a bond originator, a conveyancing attorney and a tax practitioner.

No warranty. Buy Box is provided as is and as available, without any warranty. It may contain errors, and it may change or stop working at any time.

Limitation of liability. To the extent the law allows, the operator of Buy Box is not liable for any loss or damage that comes from using it or relying on it, including any investment loss.

Fair use. Don't use Buy Box to break the law, or try to disrupt or damage the site.

Changes. These terms may be updated. The date above shows the latest version.

Law. These terms are governed by the law of the Republic of South Africa.

Contact. Questions, problems or ideas: send feedback, or open an issue on the Buy Box project page.

Privacy notice

Last updated 3 October 2026

What we collect: nothing. Buy Box has no accounts, sign-up forms, cookies, analytics, trackers or adverts. We don't receive your deals, your targets or anything you type.

Where your deals are kept. Everything you enter is saved only in this browser, on this device (in its local storage). It stays there until you delete it or clear your browser data. The site is built so that it can't send your deals anywhere.

Backups. Exported files are saved to your device. You decide where they go and who sees them. Only import files from people you trust.

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Your rights. South Africa's Protection of Personal Information Act (POPIA) gives you rights over your personal information. Because we don't collect any that identifies you, there is nothing for us to share, correct or delete. To remove everything from your device, delete your deals or clear this site's data in your browser. For questions, use the contact link above.