How to avoid expensive mistakes
Because excitement is not an investment strategy
You’ve found a property that looks perfect.
Great photos. Sensible price. An estate agent who suddenly feels like a close personal friend.
It’s tempting to jump straight in and make an offer.
Don’t.
I understand the buzz — I’ve been there. You start mentally spending rental income before you’ve even booked a second viewing. But buying without proper due diligence is a bit like getting married after a first date. It can work… but the odds aren’t exactly stacked in your favour.
Strip away the jargon and due diligence is simple. It’s about answering one question properly:
Is this property actually worth buying — for you — before you commit serious money?
In this guide
What Are We Really Checking?
Good due diligence answers four questions clearly:
What's it actually worth?
Asking price is just an opinion — often an optimistic one.
What will it realistically rent for?
Not what you hope. Not what the agent says. What the market will pay.
Does it make sense for you?
A great deal for someone else can be a terrible deal for you.
Are there any hidden problems?
Because discovering major issues after exchange is painful and expensive.
Get these right and you dramatically improve your odds of success. Get them wrong and you're gambling.
Let's walk through each one properly.
Step 1: What’s the Property Actually Worth?
You can't spot a good deal if you don't understand market value.
Market value is not:
- the asking price
- what the agent tells you
- what the seller "needs"
It's what a normal buyer has actually paid for something similar, recently.
How to Find Proper Comparables
This takes time — but it's time well spent.
Here's a simple process:
- Go to Rightmove → Sold House Prices
- Search within ¼ mile of the property (expand to ½ mile if needed)
- Match property type and bedroom count
- Focus on sales from the last 6 months
- Ignore asking prices entirely
- Click into listings and check photos — "similar" needs to mean genuinely comparable
A two-bed Victorian terrace and a two-bed new-build flat are not the same asset, even if they share a postcode.
Once you've got enough data, create a realistic price range, weighting:
- recent sales more heavily
- better condition properties slightly higher
A Quick Reality Check
If something looks significantly cheaper than everything else nearby, there's usually a reason.
It might still be a deal — but only if you understand why it's cheap.
If you can't confidently determine value because prices vary wildly or data is thin, walking away is often smarter than guessing.
Step 2: What Will It Rent For?
If you're buying to let, this isn't optional — it's fundamental.
Unlike sold prices, there's no perfect rental database, so you need to be current and realistic.
Finding Rental Comparables
Back to Rightmove — this time the rent section.
- Include properties marked "Let Agreed"
- Match size, type, and location as closely as possible
- Ignore obvious outliers (short lets, house shares, neglected stock)
Pay attention to why rents differ:
- condition
- parking
- outdoor space
- transport links
- furnishing
Understanding these patterns lets you position your property correctly.
Speak to Local Letting Agents
This is one of the most underused steps.
Call two or three local agents and ask:
- what similar properties achieve
- how quickly they let
- what tenants prioritise
They'll usually talk freely — they're hoping you'll instruct them later.
If you do this properly, you should be able to estimate rent within £50.
Step 3: Does This Deal Actually Suit You?
This is where spreadsheets meet reality.
A deal can look good on paper and still be wrong for your situation.
Know Your Numbers
Once you've got value and rent estimates, you can calculate yield — but yield alone is meaningless.
Factor in:
- mortgage payments
- insurance
- management
- maintenance
- voids
- tax (under current rules)
Mortgage interest relief is no longer what it once was. If your numbers rely on outdated assumptions, they're wrong.
Know Your Goals
Ask yourself:
- Are you chasing income?
- Capital growth?
- A balance of both?
Your strategy should dictate the deal — not the other way around.
A low-yield property in a strong growth area may be perfect for one investor and completely unsuitable for another.
Trust Your Instincts
This might sound unscientific, but it matters.
If something feels off — the street, the block, the area — pause. Often your gut is picking up details your spreadsheet hasn't noticed yet.
Step 4: Hidden Problems & Nasty Surprises
You can recover from slightly overpaying.
You can recover from optimistic rent assumptions.
Recovering from structural or legal problems is much harder.
Get a Proper Survey
A RICS survey is often money well spent.
- Level 1: suitable for most modern properties
- Full structural survey: older buildings or anything with visible concerns
Yes, it costs money. And yes, you might walk away after paying for it. That's still cheaper than discovering subsidence once you own the place.
Surveys also give you leverage — issues can justify renegotiation.
Legal Due Diligence (Let Your Solicitor Earn Their Fee)
Your solicitor will check:
- title
- covenants
- restrictions
- planning issues
For leaseholds, pay close attention to:
- lease length (under 80 years is a red flag)
- ground rent
- service charges
- upcoming major works
Leasehold surprises are rarely pleasant.
Check It's Mortgageable (Even If You're Paying Cash)
Always ask: could this be mortgaged later?
If not, your exit options shrink dramatically.
Common problem areas:
- high-rise ex-local authority blocks
- flats above commercial units
- non-standard construction
- certain postcodes with lender blacklists
Liquidity matters.
A Simple Due Diligence Framework
- Research sold comparables
- Estimate realistic rent
- Run headline numbers
- Check it fits your strategy
After Offer Is Accepted
- Instruct solicitor
- Arrange survey
- Progress mortgage
- Review legal pack
- Recheck numbers before exchange
Red Flags Worth Respecting
- Price far below comparables with no clear reason
- Thin or inconsistent rental market
- Structural concerns in the survey
- Complex or expensive lease terms
- Planning or title complications
The Stuff No One Tells You
Estate agents are not your allies.
Friendly, yes. On your side? Rarely. Verify everything.
Perfect properties don't exist.
The question is whether issues are manageable or terminal.
Walking away is often the right decision.
I've walked away after spending money on surveys — never regretted it.
You should reject far more deals than you buy.
If you're not saying no regularly, you're probably not being selective enough.
Final Thought
Due diligence can feel slow, cautious, even boring — but it’s what separates investors from gamblers.
The property market is full of people who skipped the “boring bits” and paid for it later. Don’t be one of them.
Take your time. Ask awkward questions. Double-check the numbers. Build a good team around you. And trust your instincts when something doesn’t stack up.
There will always be another property.
Opportunities don’t disappear — but bad decisions can stick around for decades.
If this one doesn’t work, move on. The right deal will wait for you.
Ready to apply this knowledge?
Join the community to get support, ask questions, and start building your portfolio the right way.
Join the Property Network
