Every London property investor eventually faces the same question: keep the house as a single let, or convert it into an HMO?

On paper, the HMO wins on yield every time. Room-by-room letting generates significantly more rental income from the same property. But yield isn’t the only thing that matters. Conversion costs, management demands, regulatory complexity, and risk profile all factor in.

This guide puts both strategies side by side using real 2026 London figures, so you can see exactly where the numbers land.

The Yield Gap: Still Significant

The core maths hasn’t changed. HMOs generate more rental income than single lets because you’re charging per room rather than per property. What has changed is the cost of getting there.

Standard buy-to-let properties in London currently deliver gross yields of around 4–5.5%. The average across the capital sits at roughly 5.1%, up slightly from 4.9% in 2025. That’s the reality of high property prices compressing returns.

HMOs in London typically deliver gross yields of 6.5–8%, with well-optimised properties in strong locations pushing higher. Nationally, HMO yields run at 8–12%, but London’s elevated purchase prices bring the percentage down even though the absolute rental income is among the highest in the country.

	Single Let (3-bed house)	6-Bed HMO
Purchase price	£450,000	£450,000
Conversion cost	Minimal (£5–10k refresh)	£80,000 – £140,000
Total investment	£455,000 – £460,000	£530,000 – £590,000
Monthly rent	£1,800 – £2,200	£5,100 – £7,200
Annual gross income	£21,600 – £26,400	£61,200 – £86,400
Gross yield	4.5% – 5.5%	6.5% – 8%+

The income gap is clear. On the same £450,000 property, an HMO can generate two to three times more monthly rent. But the HMO also requires £80–140k in conversion costs upfront, so the total capital deployed is significantly higher.

Running Costs: Where the Gap Narrows

Gross yield tells one story. Net yield tells another. HMOs carry higher operating costs, and that’s where the comparison gets more nuanced.

Management. A single let is simple. One tenant, one AST, one relationship. Many landlords manage single lets themselves. HMOs are more hands-on: six tenants, six contracts, more maintenance requests, higher turnover. Professional management typically costs 10–15% of gross rent, which on a £5,100/month HMO is £510–£765 per month.

Bills. Single-let tenants usually pay their own utilities. HMO landlords often include bills to attract tenants and simplify management. For a six-bed London HMO, council tax, gas, electric, water, broadband, and communal cleaning can run £800–£1,200 per month.

Maintenance. More tenants means more wear on kitchens, bathrooms, and communal areas. HMO maintenance budgets run roughly 50–75% higher than a comparable single let.

Licensing and compliance. HMOs need a mandatory licence (£500–£1,500 per five-year cycle), annual gas safety certificates, electrical inspection reports, fire risk assessments, and ongoing fire safety equipment checks. Single lets have fewer ongoing compliance obligations.

After all expenses, a well-run London HMO typically delivers a net yield of 4–6%. A single let might net 3–4.5%. The HMO still wins, but the gap is narrower than the gross figures suggest.

Risk: Different Profiles, Not Better or Worse

The risk profiles of each strategy are genuinely different, not just a question of “more risk, more reward.”

Void risk. This is where HMOs have a clear structural advantage. If your single-let tenant leaves, you lose 100% of your income until you find a replacement. In a six-bed HMO, one empty room costs you roughly 17% of income. The remaining five rooms keep paying. Rental income is diversified across multiple tenancies, which provides a natural buffer.

Regulatory risk. HMOs face more regulation: mandatory licensing, additional licensing in many boroughs, Article 4 Directions, stricter fire safety standards, and the new Renters’ Rights Act provisions coming into force in May 2026. Non-compliance can trigger fines of up to £40,000 per offence, criminal prosecution, and rent repayment orders. Single lets are simpler to keep compliant.

Market risk. Both strategies are exposed to rental market conditions, but HMO demand in London has been consistently strong. Young professionals are increasingly priced out of renting whole properties, driving sustained demand for quality shared accommodation. The cost-of-living pressure has, if anything, strengthened the HMO tenant pool.

Financing: A Different Market

Standard buy-to-let mortgages are widely available from mainstream lenders, typically requiring a 25% deposit. HMO mortgages are more specialist. They usually require a 25–35% deposit, and lenders assess the property on a room-by-room rental basis.

In early 2026, the Bank of England base rate sits around 3.25–3.75%, with typical buy-to-let fixed rates in the mid-4% range. HMO-specific rates tend to run slightly higher, but the stronger rental income means HMOs often pass lender stress tests more comfortably than single lets on the same property.

Which Strategy Suits You?

Single lets work best for investors who want simplicity, lower upfront costs, and minimal management hassle. If you’re building a portfolio of clean, straightforward assets and you value low maintenance over maximum yield, single lets are the sensible choice. They’re also the right starting point if you’re new to property investment and want to learn the basics before stepping up.

HMOs work best for investors who want to maximise income from each property and are willing to deal with the additional complexity. The higher upfront conversion cost, the regulatory requirements, and the management demands all need to be factored in honestly. But for those who approach it properly, the return on capital is substantially higher.

The worst decision is somewhere in the middle: converting a property into an HMO but cutting corners on compliance or management. That’s where the losses happen.

The Renters’ Rights Act: Affects Both Strategies From May 2026, Section 21 no-fault evictions are abolished for all tenancies. Both single-let and HMO landlords will rely on strengthened Section 8 grounds to regain possession. The maximum civil penalty for housing offences rises to £40,000. Professional documentation and robust tenancy management are now essential regardless of which strategy you choose.

How hmoconversionbuilders Can Help

If you’re looking at HMO conversion, the quality of the build determines whether those higher yields actually reach your bank account. A compliant, well-designed conversion lets smoothly and passes inspection without fuss. A rushed job costs you twice.

At hmoconversionbuilders, we handle the full conversion process: feasibility assessment, layout design, planning support where needed, and the complete build to licensing-ready standard. Every project is designed to pass inspection first time and start generating income on schedule.

Get in touch for a free, no-obligation consultation. We’ll help you work out whether an HMO conversion is the right move for your property.

Disclaimer: This article is for general informational purposes only and does not constitute financial or investment advice. Property values, rents, yields, and costs vary by location and can change. Always carry out your own due diligence and consult qualified professionals before making investment decisions.