See how a property purchase actually works — the mortgage, the equity, the tax, and what could go wrong. Edit any figure to match a scenario you're weighing up.
⚠️This is illustrative, not personal advice. Stamp duty, Capital Gains Tax and mortgage products all depend on your exact circumstances, and rates change. Check current HMRC and lender figures — or speak to a professional — before acting on any number shown here.
Who's buying
Your ownership share50% / 50%
Deposit, costs, mortgage payments and equity are assumed to be split in this ratio. Adjust if you're not splitting 50/50.
First-time buyer relief applies to both scenarios below, since neither involves owning another property.
Property & mortgage
Loan-to-value: 80.0%
0%75% (best rate tier)100%
⚠️ Deposit + loan doesn't match the purchase price — check your figures. Loan cannot exceed price minus deposit.
Deposit is 20.0% of the purchase price · your share of the deposit: £25,000
Buying costs & renovation
Excludes stamp duty — calculated below
What you spend on the works
Uplift in property value
Stamp duty at your FTB status: £0
Assumptions
Interest rate4.5%
Mortgage term25 yrs
Hold period before sale5 yrs
Annual growth assumption3.0%
Overpayment (combined, monthly)£0
Required payment
£0/mo
total, standard terms
Total paid
£0/mo
standard only
Your payment
£0/mo
your share
Key numbers at exit (Live in, then sell basis)
Sale price
—
—
Mortgage left
—
LTV at exit: —
Your equity
—
your share
Interest paid
—
your share, sunk cost
Inflection point
—
—
💡
Why the inflection point matters. Early in any repayment mortgage, most of each payment is interest — the cost of borrowing — not equity. The inflection point is the month that flips: more than half of each payment starts reducing what you owe, rather than disappearing as interest. Before it, you're mostly renting the bank's money. After it, you're mostly building an asset. This matters most if you're planning to sell within a few years, because it directly shapes how much of what you've paid in comes back to you as equity versus how much is gone for good. Overpaying — even a modest amount — brings this point forward, which is why it's shown here rather than left as a footnote.
Month 1: — of your payment builds equity. By the end of your hold (yr 5): — goes to equity.
% of each payment building equity, over your hold
With overpaymentStandard payment only50% threshold
Mortgage balance over the hold period
With overpaymentStandard payment only
What happens to your money
Comes back at sale — not a real cost
Deposit (your share)
£0
Renovation spend (your share)
£0
Principal repaid over hold (your share)
—
Gone for good — true sunk cost
Stamp duty + buying costs (your share)
£0
Interest paid over hold (your share)
—
Total true sunk cost, your share
—
🏠
Two ways this purchase could play out — living in it, or becoming an accidental landlord by letting it out instead. Each has a different tax treatment. This isn't personal tax advice — Capital Gains Tax depends on your full circumstances, and rates change. Check current HMRC figures or speak to an accountant before relying on these numbers.
Capital Gains Tax band (applies to Let out — never to Live in)
Your rate depends on your total income for the year — many landlords with rental profit sit in the higher band. Uses the 2025/26 annual exempt amount of £3,000 per person; check the current figure before relying on this.
Live in, then sell No CGT
At completion
Sale price
—
Mortgage cleared
—
Sale costs
—
Your P&L
Equity received
—
Less: sunk cost
—
Net position
—
—
Let out, then sell CGT applies
Rental over hold
Monthly surplus
—
Total surplus
—
Then sell
Sale position
—
CGT (estimate)
—
Net position
—
—
Net position — with vs without overpayment
With overpaymentStandard payments only
🔓
See your full exit numbers
Unlock the Let out scenario, the CGT estimate and the Stress Test — free, takes ten seconds.
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⚠️
Every number so far has assumed things go roughly to plan. They often don't. This tab shows both scenarios under pressure — a rate rise, an empty property, a fall in price — shown together as a genuine bear case, not a footnote. If a scenario only looks acceptable when everything goes right, that's worth knowing before you commit.
Rate rises by+2.0%
Void period (no rent, rental scenarios only)2 mo
Price falls by, at sale10%
The stressed case also assumes overpayments stop — a squeezed budget is the point of a stress test.
Live in, then sell
Base case
—
your equity at exit
Stressed
—
your equity at exit
What changes
—
Let out, then sell
Base case
—
net position
Stressed
—
net position
What changes
—
🔓
See the bear case
Unlock the rate-rise, void-period and price-fall stress test — same details as above, only need to enter them once.
We'll only use this to follow up on your enquiry — no spam, unsubscribe any time.
How this is built: one mortgage · figures split by your ownership share, editable above · loan auto-syncs when deposit changes · SDLT calculated on current England & Northern Ireland rates from 1 April 2025 (0%/2%/5%/10%/12% bands; FTB relief 0% to £300k then 5% to £500k, no relief above £500k) — Scotland (LBTT) and Wales (LTT) are not modelled here and use different bands · renovation spend is treated as adding directly to property value at purchase, then growth compounds from that new base · inflection point = the month the principal portion of your actual payment first exceeds the interest portion · overpayments reduce balance directly (assumes no early repayment charge — check with your lender) · Live in assumes the property is your main residence throughout, so Private Residence Relief applies and no CGT is due · Let out assumes it's never your main residence, so the full gain is taxable, less your annual exempt amount, at the band selected · sale costs assumed at £3,000 combined · this tool is for illustration only, is not personalised financial or tax advice, and real transactions involve costs and rules not modelled here in full.