You need fewer numbers than you think
Deal analysis has a reputation for being a spreadsheet nightmare. It isn't. Most experienced investors run the first pass on a deal in a couple of minutes with a handful of numbers. The detailed spreadsheet comes later, only for deals that survive the quick sniff test.
Here's a simple, repeatable framework you can use on any UK property.
Step 1 — Start with the rent, not the price
Beginners fixate on the purchase price. Investors start with **what it will realistically rent for**, because rent drives everything.
- Find what comparable properties actually let for nearby — same size, same
type, same street if possible.
- Use a conservative figure. If the range is £850–£950, model £850.
If you can't find solid rent evidence, that's your first red flag — you're guessing, not analysing.
Step 2 — The quick yield check
Gross yield is your fast filter for whether a deal is even worth a closer look:
Gross yield = (annual rent ÷ purchase price) × 100
So £9,000 annual rent on a £120,000 property is a 7.5% gross yield. This won't tell you if a deal is good, but it instantly tells you if it's in the right ballpark or a waste of time. Deals well below your area's norm usually don't survive the next steps.
Step 3 — The numbers that actually matter: monthly cash flow
Gross yield ignores costs, so now do the honest version. Work out what's left each month after everything real:
- Mortgage payment (use today's rates, not last year's).
- Insurance.
- Maintenance allowance — set aside a slice of rent every month; things break.
- Management — even if you self-manage, cost it as if you didn't, so the deal
stands on its own.
- Voids — budget for the property being empty part of the year.
Rent, minus all of that, is your real monthly cash flow. If it's comfortably positive, you have a candidate. If it's thin or negative, the deal needs a very good other reason (like strong, evidenced growth potential) to justify it.
Step 4 — Stress-test it
This is the step that separates investors from optimists. Ask:
- What happens to cash flow if interest rates rise a percentage point or two?
- What if the property sits empty for two months?
- What if you hit a £2,000 repair in year one?
A deal that only works when everything goes perfectly is not a good deal — it's a fragile one. A good deal bends under stress but doesn't break.
Step 5 — Look for the red flags
Numbers aside, sense-check the property itself:
- Very cheap for the area? Find out why before you get excited — it's
usually a reason, not a bargain (short lease, structural issues, bad location).
- Short lease on a flat? Extending can be expensive; factor it in.
- Reliant on an unusually high rent to work? Be sceptical.
- Major works looming (roof, damp, rewire, cladding)? Get quotes before you
commit, not after.
How to know when the numbers "work"
You don't need certainty — you need a deal that clears three simple bars:
- Positive cash flow on conservative, real-world numbers.
- Survives the stress test without falling apart.
- No unexplained red flags you haven't priced in.
Hit all three and the numbers work. That's genuinely it. You don't need a 20-tab spreadsheet or a finance degree — you need to be honest with your inputs and disciplined about walking away from deals that don't clear the bars.
The one habit that matters most: analyse many deals and buy few. The
"no" is where your money is protected. Most properties you look at should be a
polite pass — and that's exactly how it's supposed to feel.
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A quick, honest note. This guide is general property education, not
regulated financial, mortgage, tax or legal advice. Everyone's situation is
different, so before you commit money, speak to a qualified professional who
can look at your specific circumstances. We'll always tell you when something
is worth a proper conversation with an expert.