Diamond However the rest of your post is absolute nonsense. How is a landlord subsidising the tenant? It's very unusual to rent a house for less per Calendar month than the mortgage would be
See VivaLeBeaver's post above.
That's on a tiny mortgage. Say on a more typical example of a btl landlord putting down a 15% deposit of a £250,000 house with 3 bedrooms in a city in the UK. A very rough suggestion of costs (not including purchase costs of stamp duty and legal costs):
Mortgage: £1300 per month.
Agency fees: 10-15%
Start up costs - gas safety certificate, EPC, private landlord registration, drawing up lease, tenant checks, tenant move-in fees, etc. - up to £1000 as a one off every time the tenant changes or every year
If in Scotland and an HMO - HMO license every year about £350, plus complying with the changing standards - budget a £1500 per year plus fire extinguisher checks annually plus replacement every 5 years. Recently Edinburgh introduced a requirement that all HMOs had to be carpeted - so as an unexpected one off cost of covering hardwood floors, maybe another £1000.
Say you rent each room to unrelated persons for £500 per month - doubtful you would be in profit but maybe, just maybe for two months of the year, you might make a couple of hundred.
That's not including costing your own time and unexpected repairs of course! Complying with the necessary paperwork takes up a lot of time - especially since a landlord recently, whose agent got the postcode slightly wrong when registering the deposit was fined the entire deposit, in one of the most unfair decisions of the courts I can recall hearing. It also means that landlords are running a proverbial knife-edge, bearing the risk of massive fines (more than if they went out drink driving and killed someone) for small clerical errors through no fault of their own.
If you do make a few hundred, remember that if you are a higher rate taxpayer, paying the mortgage out of your already taxed income, you will be charged 40% on that. Although you can claim a wear and tear discount of 15%.
Of course, there may be those who were gifted properties, or lots of money, but many small btl landlords seem to have jobs. Perhaps we should have a public register of everyone's financial resources, so we can all decide whether they are worthy enough or not (some countries do - e.g. Norway, Denmark - your entire salary and income and tax payments are published nationally, online, in public).