How to Analyse an HMO Deal: The Numbers That Actually Matter

HMOs look brilliant on the back of an envelope. Five rooms at £550 a month reads like £33,000 a year against a mortgage that a single-let landlord would kill for. Then the first void hits, the utility bills land, the licensing officer visits, and the envelope maths quietly falls apart.

The difference between HMO investors who compound and HMO investors who exit bruised is rarely the property — it's the quality of the analysis before purchase. Here's a framework that holds up.

Step 1: Verify the property can legally be an HMO

Before any yield maths, three checks that kill more deals than price does:

• Article 4 directions. Many councils have removed permitted development rights for small HMOs (C3→C4 conversion), meaning you need planning permission that may simply not be granted. PropCalc's HMO analyser flags Article 4 coverage for the postcode when enrichment runs — still verify the specific street with the council, because boundaries are drawn tightly.
• Licensing. Mandatory licensing applies to HMOs with 5+ occupants from two or more households; many councils run additional and selective schemes that catch smaller HMOs too. Licence conditions dictate minimum room sizes (typically 6.51m² for a single adult bedroom), amenity ratios, and fire safety spend.
• Room sizes and layout. Measure, don't assume. A "5-bed HMO" with one room under the minimum is a 4-bed HMO with worse economics, and a lounge conversion may push you into planning territory.

If the deal only works with the questionable fifth room, it doesn't work.

Step 2: Build revenue from evidenced room rates

Get actual advertised and achieved rates for comparable rooms in the same postcode — same standard of finish, same bills-included structure. Then model realistic occupancy, not 100%. Well-run HMOs in strong areas still see 4–8% voids from tenant churn and re-let gaps; student HMOs may have structural summer voids. A five-room HMO at 95% occupancy loses roughly one room-month every four months — put it in the model.

Step 3: Use HMO operating costs, not single-let costs

This is where most HMO analysis fails. A single let might run at 10–15% operating costs; an HMO with bills included does not. Model each line:

• Utilities (gas, electric, water) — tenants who don't pay the bill don't economise on the heating
• Broadband, TV licence
• Council tax (owner's responsibility in an HMO; note some councils are moving to band or re-band rooms individually)
• Cleaning of common areas, gardening
• Licensing fees amortised over the licence period, plus certificates: gas safety, EICR, fire alarm servicing, emergency lighting, PAT
• Maintenance — materially higher per property than a single let; five tenants generate five tenants' worth of wear
• Management: 10–15% for full HMO management if you're not self-managing (and your time isn't free either)
• Insurance (HMO-specific policy), rent protection if used

A realistic all-in operating ratio for a bills-included HMO commonly lands between 30% and 40% of gross rent. If your spreadsheet says 18%, your spreadsheet is lying to you.

Step 4: Model the debt properly

Run the numbers at today's achievable HMO mortgage products, not the best rate you've ever heard of. Then stress-test: if your product rate rose by 2 percentage points at refinance, does the deal still cash flow? Lenders will also stress your rent for affordability (ICR) — a deal that passes your test but fails the lender's isn't financeable at your assumed leverage.

Factor the EPC position too: rented homes are heading for a minimum EPC C by 2030 under the government's current plans, so a D-or-below HMO carries a known future capex bill. Price it now, not later.

Step 5: Judge the deal on four numbers

1. Net monthly cashflow after all operating costs, voids, and finance — not "rent minus mortgage."
2. Net yield on total money in (purchase + refurb + fees), not gross yield on price. Gross yield is a marketing number.
3. ROI on cash employed — after any refinance, what return does the cash actually left in the deal generate?
4. Cash left in after refinance — for recycling strategies, the deal's true cost is the cash you can't pull back out.

A strong HMO deal survives all four with conservative inputs. A weak one needs 100% occupancy and 2019 utility prices to break even.

A worked sanity check

Five rooms × £550 = £2,750/month gross. At 95% occupancy: £2,612. Operating costs at 35%: −£914. Mortgage on a £180k facility at a stressed rate: call it −£1,050. Net cashflow ≈ £648/month — a real deal, but a third of what the envelope promised. That's the number to underwrite, and the number to compare against the next deal.

Analyse in minutes, not evenings

PropCalc's HMO mode runs this full stack — room-by-room income, itemised operating costs, refurb budget, bridge-to-term finance, and Deal Verdict's maximum-price-for-target-return — against the property's real listing history, EPC rating, council tax band, and Article 4 status. Start your free 7-day trial and stress-test your next HMO before you offer.

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FAQ

What's a good yield for an HMO? Gross yields of 10–15% are common headline figures, but the honest metric is net yield on total cash invested after true HMO operating costs — strong deals typically clear 8%+ net. Anything assessed on gross yield alone should be treated as unanalysed.

Do I need a licence for a 4-bed HMO? Maybe — mandatory licensing starts at 5 occupants, but many councils operate additional licensing schemes covering smaller HMOs. Always check the specific council, and check for Article 4 directions at the same time.

Should I include voids in my analysis? Always. Even excellent HMOs churn tenants; 5–8% of gross rent is a sensible allowance, more for student lets with summer voids.

Calculations in this article are illustrative estimates only and do not constitute financial, legal, or investment advice.