How to Spot a Bad Buy to Let Deal

A bad buy to let deal usually announces itself in four ways: a gross yield quoted with no cost model underneath it, a rent figure lifted from a portal listing rather than from achieved comparables, a refurbishment costed per square foot instead of itemised, and a street that looks perfectly fine on a map. Any one of those is a reason to slow down.

None of these are exotic. They’re in most deal packs I get sent, including ones from businesses charging real money to produce them.

Bullseye Properties Ltd is a buyer-only sourcing business across South Yorkshire and North Nottinghamshire. Most of what I look at never reaches a client, and it fails on the four things below more often than on anything structural.

Tell one: a gross yield with nothing underneath it

Gross yield is annual rent divided by purchase price. That’s it. It contains no costs at all, which makes it useful for a first filter and useless for a decision.

Take a real shape of deal. £75,000 purchase, £650 a month rent. That’s £7,800 a year, so 10.4% gross. It reads beautifully.

Now put the costs in.

Line	Amount
Gross rent	£7,800
Management at 10%	£780
Maintenance allowance at 10%	£780
Insurance	£250
Void allowance at 4%	£312
Gas safety, EPC, electrical checks amortised	£200
Net rent before finance	£5,478

Cash in on a 25% deposit is £18,750, plus £3,750 of stamp duty at the higher rates, plus legals, survey and mortgage arrangement. Call it £26,000. Mortgage interest on £56,250 at 5.5% is £3,094. So the actual cash return is £2,384 on £26,000, which is 9.2% before tax.

That one happens to survive, which is the point. The gross number told you nothing about whether it would. A different property with the same 10.4% gross and a £180 a month service charge on a leasehold flat lands somewhere completely different, and the headline is identical.

The test: if a pack shows you a percentage without showing you the deduction list that produced it, the percentage isn’t a finding. It’s a division sum.

Tell two: the rent came from the listing, not from what people actually pay

This is the one that quietly ruins the most deals, because everything downstream is built on it.

Rents advertised on portals are asking rents. They tell you what a landlord hoped for. They don’t tell you what was achieved, and they don’t tell you the property sat empty for nine weeks first. If you build a model on a £700 asking rent and the street actually lets at £625, you’ve overstated the annual income by £900 and understated the void risk at the same time.

What a real rent figure looks like: three to five properties of the same type, same bed count and comparable condition, within roughly half a mile, that have actually been let in the last twelve months, with the dates. Plus a note on how long each one was advertised. If two of the five sat on the market for over a month, your void allowance needs to be more than 4%.

At 55 Hunt Lane in Bentley, Doncaster, the rent of £650 a month against a £61,500 purchase gives 12.7% gross. That figure is only worth anything because the £650 is what the property lets for, not what a listing asked for.

The test: ask where the rent number came from. “Similar properties on Rightmove” is not an answer.

Tell three: the refurbishment is costed per square foot

Per square foot refurb costing is a shortcut used by people who haven’t been in the building. An 800 square foot terrace at £40 a foot gives you £32,000, and that number has the confidence of arithmetic and the accuracy of a guess.

Works don’t scale with floor area. A rewire is priced on circuits and sockets. A damp proof course is priced on linear metres of affected wall. A roof is priced on the roof, which has nothing to do with how many bedrooms are under it. Two identical terraces on the same street can be £6,000 apart because one has a failed chimney flashing.

What an honest refurb figure looks like is a line by line schedule with a contingency on the end. Typical ranges on a small two or three bed terrace in this region, and these do move with the property and the trade:

Item	Typical range
Full rewire and new consumer unit	£4,000 to £5,500
Boiler and full central heating	£3,500 to £4,500
Damp proof course and replastering to affected walls	£2,000 to £3,500
Re-covering a pitched roof	£6,000 to £9,000
Kitchen supplied and fitted	£3,000 to £4,000
Bathroom supplied and fitted	£2,500 to £3,500
Plaster, decorate and flooring throughout	£6,000 to £8,000

Add 10 to 15% contingency. On a £25,000 schedule that’s £2,500 to £3,750 you should assume you’ll spend, because on older stock you usually do.

The test: ask for the schedule. If the answer is a single round number, nobody has priced it. They’ve estimated it, and you’re carrying the difference.

Tell four: the street looks fine on a map

A map shows you a road, a school, a park and a Tesco. It doesn’t show you which end of the road the trouble is on, and in this region that changes over a distance of about 200 metres.

Doncaster is the clearest example. Two streets in DN4 can produce completely different void rates, arrears and price growth while sitting in the same postcode district and looking identical on a satellite view. Postcode level crime statistics average those two streets together and hand you a number that describes neither of them.

The honest version: I wouldn’t let my dog live on some streets. Those streets also probably won’t go up in value, and the two things are the same thing. High yield in a low demand street isn’t a bargain, it’s the market pricing risk correctly.

What actually tells you: standing on it. Failing that, street level crime data rather than area data, checking who the employer is that would put a tenant there, looking at how many properties on the same street are currently for sale or to let at once, and looking at Land Registry price paid data for that specific street over ten years. If houses there sold for £68,000 in 2015 and £74,000 now, that’s under 1% a year, and no yield figure changes what that means.

Tell five: “below market value” measured against the asking price

An asking price is a marketing number. A discount against it is a marketing number too.

23 Beech Grove was first listed at £125,000, reduced to £109,500, and bought at £90,000. Against the original asking price that’s 28% off. Against the reduced asking price it’s 18%. Against comparable sold prices it’s whatever the comparable sold prices say, and that’s the only one of the three that means anything.

The test: ask for the sold comparables that establish market value, not the price history of the listing. Three to five, same street or immediately adjacent, sold in the last six to twelve months, adjusted for condition. If the pack says “20% BMV” and the evidence is a struck through asking price, the discount is on the marketing, not on the property.

Tell six: the things that were left out

Bad packs are usually more identifiable by absence than by anything they contain. The list I check for:

• No EPC rating, or a D and no route to C costed. The compliance date for the new EPC C standard in the private rented sector is 1 October 2030, with a £10,000 per property cost cap, per the GOV.UK government response published 21 January 2026, checked 25 August 2026.
• No tenure line. Leasehold with 78 years left and a £1,400 service charge is a different asset to the freehold next door at the same price.
• No flood check. Across South Yorkshire, with the River Don and its tributaries, this isn’t optional.
• No mention of Article 4 direction where the pitch involves an HMO (House in Multiple Occupation). Much of Sheffield is covered, which restricts conversion.
• No void allowance in the model at all. A model with zero voids is a model of a property that never has a tenant leave.
• No photograph of the rear elevation or the street. Agents photograph the lounge with a wide angle lens. Nobody photographs the back of the house by accident.

What a good deal pack contains

Short version, and you can hold any pack up against it:

1. Purchase price with three to five sold comparables behind the claimed market value
2. Achieved rents with dates and time on market, not asking rents
3. A full deduction list to a net figure, with a void allowance stated
4. Itemised refurb schedule with contingency, from someone who has been inside
5. EPC rating and the costed route to C
6. Tenure, service charge, ground rent, lease length
7. Flood and street level crime, not area averages
8. The stress test at the current mortgage rate plus 1.5 to 2%
9. Whatever is wrong with it, written down

That last one is the real filter. Every property has something wrong with it. A pack that doesn’t name anything either hasn’t looked or isn’t telling you.

What I would do next

Take the last deal pack you were sent and go through the six tells above. Most packs fail at tell one and tell two, and they fail in the same direction, which is optimistic.

Then ask the person who sent it the awkward question: who else is paying you on this transaction. Five questions every investor should ask before buying has the other four, with my own answers to all of them.

If you want a second opinion on a specific property, send it to me. I’ll build the cost model and tell you what I’d do, including if the answer is leave it. How it works sets out the process, and the case studies show what survived it.

Connor, Bullseye Properties Ltd