## The checks that come before yield
HMO investors often begin with room rent because the gross yield looks higher than a single let. That is the wrong first step. Start with whether the property can lawfully operate as the intended HMO. GOV.UK explains [HMO licensing](https://www.gov.uk/house-in-multiple-occupation-licence), and the [Housing Act 2004](https://www.legislation.gov.uk/ukpga/2004/34/part/2) is the key legislative framework.
Planning is separate. Article 4 directions, sui generis use, and local standards can change the answer, so check the council before you price the deal.
## The HMO underwriting stack
Model:
- Purchase price, tax, legal fees, and finance costs.
- Licence fees, fire works, room-size compliance, and amenity works.
- Room rent evidence by room type.
- Utilities, council tax, broadband, cleaning, maintenance, management, and voids.
- Mortgage stress, ICR, lender appetite, and refinance value.
- Exit route if the HMO market weakens.
Gross rent is only one line. Net income after the operating stack is what supports value and debt.
## Worked example
A five-room HMO produces 3,250 per month gross rent, or 39,000 per year. Operating costs, utilities, management, maintenance, and voids total 11,000. Net operating income is 28,000 before finance.
If a seller presents the deal at a 9 percent gross yield, ask what the net yield is after costs and what the lender will accept for rent. If the stress test caps borrowing below the planned loan, the purchase price must change.
## Common mistakes
The most common mistakes are ignoring additional licensing, using best-case room rents, underestimating utilities, assuming income valuation at refinance, and treating management as free. HMOs can be strong investments, but they are operational assets. The model should reflect that.
## Better next step
Build the HMO model from compliance outward. If licensing, planning, rent proof, operating costs, and finance all work, then compare the HMO with single-let or serviced-accommodation alternatives. If one of those checks is missing, keep the offer conservative until the evidence is real.
## What to save in the model
For this hmo property investing: underwriting basics check, save the source links, date checked, calculator inputs, base case, downside case, professional question, and final pass or proceed decision in the deal notes. Also save who verified each assumption: broker, solicitor, council, insurer, accountant, or your own viewing notes. The article should not be the evidence itself. It is the checklist that tells you which evidence to collect, where to link it, and which calculator result changed the decision. For live deals, rerun the model whenever one assumption changes. If the answer changes, update the offer price before sharing the pack. Keep rejected assumptions visible too.