Deal calculator

Work out stamp duty, the cash you need, yield, cash flow and return for a buy-to-let, HMO, flip or BRRR deal. Open it from any home or postcode to fill in our estimate, the floor area, local rents and Local Housing Allowance. New to these? Read the strategy guides.

Let rooms to separate tenants who share a kitchen or bathroom. Pre-filled for 30, Westminster Drive; change anything.

−£327Cash flow a month

3.3%Net yield

-1.3%Return on cash

The homePurchase priceour estimate today; use the asking priceWhereRefurbishment149 m² (1,604 sq ft) floor area, energy rating D

Rough 2026 starting points, not quotes.

Buying costsLegal feesSurveyOther

MortgageLoan to value%Interest rate%Lender and broker feesType

LettingLettable roomsRent per room a monthShared-room LHA here: £595 a monthBills you pay a monthenergy, water, broadband, council taxLicensing, yearly sharelicence fee divided by its yearsVoids%Letting and management%Repairs and maintenance%Insurance a yearService charge and ground rent a year

Local Housing Allowance here

Outer North London rates, 2026–27, a month: shared room £595 · 1 bed £1,150 · 2 beds £1,400 · 3 beds £1,695 · 4 beds £2,200. The most housing support a tenant on benefits can get here; a guide to the bottom of the market.

Planning

This postcode is in an HMO Article 4 area: turning a house into a small HMO needs planning permission. HMO guide

Cash in

Deposit (25% of price)	£217,250
Stamp Duty Land Tax (additional-home rates)	£76,900
Legal fees	£1,800
Survey	£600
Total cash in	£296,550

Stamp Duty Land Tax: £76,900

£0 – £125,000	5%	£6,250
£125,000 – £250,000	7%	£8,750
£250,000 – £869,000	10%	£61,900

Additional-home rates, as checked in October 2026. Buying through a company, or replacing your main home, can change this. Stamp duty calculator

A year of letting

Rent (5 rooms x £740 a month)	£44,400
Mortgage payments (interest only, 5% on £651,750)	−£32,587
Voids (5% of rent)	−£2,220
Letting and management (10% of rent collected)	−£4,218
Repairs and maintenance (8% of rent)	−£3,552
Landlord insurance	−£350
Bills you pay (energy, water, broadband, council tax)	−£5,400
Cash flow before tax	−£3,927 (−£327 a month)

Gross yield: 5.1%
Net yield (before mortgage): 3.3%
Return on cash in: -1.3%

Will a lender agree?

Lenders usually test the rent against interest at a higher “stress” rate, here 7%. Rent covers it by 125% (basic-rate taxpayers and companies): no; by 145% (higher-rate taxpayers): no. The rent supports a loan of about £507,429 or £437,438. Lenders differ.

The rent may not pass a typical lender stress test: lenders often want rent to cover interest at 7% by 125%, which caps the loan near £507,429.
With 5 or more tenants from 2 or more households, a mandatory HMO licence is needed everywhere in England; many councils license smaller HMOs too.

All figures are before income tax. Individual landlords cannot deduct mortgage interest in full (they get a 20% tax credit instead), so higher-rate taxpayers pay tax on more than their cash flow. This is a calculator, not financial advice. Read the guide

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