A house in multiple occupation earns more per square foot than the same house let to one family, which is the whole point of it. Lenders know that, and they price the extra management and the extra void risk into a higher interest cover test than a standard buy to let. The figure varies a good deal by lender and by how you hold the property.
The second difference is the valuation, and it catches people out. A valuer will usually produce two figures, the bricks and mortar value as an ordinary house and the investment value based on the rental income. Which one a lender uses varies by lender and by size: smaller HMOs are commonly valued as ordinary houses, and some lenders lend against the lower of the two. So the yield that makes the deal work may not be the number the loan is sized on.
Then there is permission. Five or more occupants forming two or more households needs a mandatory licence, many councils run additional licensing below that, and an Article 4 direction removes the permitted development right to convert, so planning is required where it otherwise would not be. Getting that order wrong is the most expensive mistake available here.
Both valuations anticipated
We establish early whether a lender will work from bricks and mortar or investment value, because on a larger HMO the gap between the two decides whether the purchase funds at all.
Licensing and Article 4 checked before an offer
Mandatory licensing, additional or selective schemes, and whether the property sits under an Article 4 direction. A lender will ask, and an unlicensed property in a licensing area is a decline rather than a condition.
Room count matched to the lender
Up to six rooms is a broad market. Above that the lender list shortens sharply and pricing moves, so knowing where the property sits in that band before you offer is worth more than a rate comparison.
Cover tested on the rent a valuer will accept
Not the gross room rate. Bills included, voids and management all sit between the advertised rent and the figure a lender will count towards its cover test.