A few have raised the issue of "tenants paying off my mortgage", and of course it's true that (hopefully) most months I make a profit from costs vs income. However, most if not all buy-to-let mortgages are interest only.
I categorically do not use the rental income to pay off capital on the mortgage - instead I am taking the risk that long term, the property value will increase and by selling one or two of them, that will pay off the mortgage on the remaining two.
The rental income is used to pay for my day-to-day living expenses, just as the person who leases you a car uses any profit to take their salary.
For those of you who are adamant that landlords are all unethical, you are of course entitled to your view. But I would ask whether you believe that all property is theft, and nobody should be allowed to profit from any type of capitalism (the logical conclusion to your argument). If this is the case, and you are full on communist, I actually admire you a little bit
.
If, however, you think it's fine that it's OK to have to pay the dental hygienist £50 when they have trained on the NHS, or if it's OK to pay for petrol, or water rates or electricity, then I'm a bit confused at what the difference is.