Personally i think the government need to introduce rent caps, i was watching something on TV the other day and they were comparing rental costs of a council house to private rent. The private rent is many multiple times higher.
I'm not saying that costs should be reduced to a point where the landlord has to pay extra for his mortgage costs, as that would destroy the rental market which people do rely on. But being a landlord shouldn't be a job with a generous income.
It's more complex than a simple rent comparison.
For a start, private landlords don't have council-tax funded departments to do decorating, repairs, maintenance, etc. Private landlords also have to either factor in a lot of time dealing with tenants, or see an agent take a cut right off the top. Private landlords also have to eat the cost of troublesome tenants, including those deliberately doing damage to force eviction proceedings for benefit reasons. Then there's the cost of replacing kitchens every few years because, generally (though with exceptions) tenants don't take care of a landlord's property the way they'd take care of it if they'd paid for it themselves. There's also the cost of property standing empty between tenants that, generally, councils don't face because they aren't paying mortgage costs regardless of occupancy.
No landlord in existance, in my experience, can charge several times market rate so the only way it's multiple times a council rent is where council rents are, for various reasons, artificially depressed.
Few landlords are making vast amounts on rent. Where they do stand to do very well, if housing price trends continue, is on capital appreciation but then, you're taking an extremely large financial risk that they will. And if you get it wrong, or time it wrong, or over-leverage, you can go from apparently very wealthy to definitely very bankrupt in a very short space of time.