But OP, in answer to your question, I don't think its possible to make a proper analysis of something without proper costs-benefits figures in front of you.
I keep hearing on here about all these profits landlords are making, and perhaps some are (particularly if they bought a long time ago and have mostly paid off their mortgages).
In reality, it goes something more like this: landlord moves out of own house for whatever reason (marriage, work) and decides to rent it. Start up costs: some new furniture, minor redecoration, gas safety certificate, EPC, landlord registration, HMO licence (if applicable, c. £600 a year where I am), agency fees (usually first months' rent).
House leases for a year to working tenants at £750 a month. Mortgage costs £500 (and that's with a big deposit). Profit = 12 x £250 = £3000, minus start up fees, so around £1800 if not an HMO lets say. Pay tax on that at higher rate, after the 15% deduction for wear and tear. Not so much a profit as enough to maintain it and the furniture, if no big costs come in such as roof repairs, cleaning up the mess left by disastrous tenants, etc.. And this doesn't include charging for time, which obviously if it were charged, would mean running at a big loss.
Then you have a void of say 10 weeks, because of timewasting potential tenants messing around. Lets just say its not exactly difficult to avoid making a profit so as to pay tax. Anyone who is efficient enough to run their business, whatever that business is, so as to regularly pay tax, is probably doing so because the alternative is running at a loss, and they don't have the personal resources to carry that loss.
As for all the criticisms of "amateur landlords" - is this not simply because in the UK we are so discouraged from actually doing anything for ourselves that someone setting themselves up as a "property expert" suddenly gains magical powers to do things better? Just look at how badly many council houses are managed and the poor standards they have got away with for years.