O
Octopus
Why a hot potato?
Because they need to be licenced / registered with the local authorities, inspected and subject to more stringent tests etc than a normal domestic property.
A single room in my patch (in a scruffy area) can easily be "worth" £500 per month, so convert the lounge and dining room and hey presto a 3 bed house is now a 5 bed HMO - so £2500 per month or £30,000 per year .....
Then there are cash payments and loss of tax revenues
I could go on