Offering people a service of housing, without having them to deal with the complexities of property purchase, financing, transaction costs, maintenance and whatnot comes with it.
Except you can pay somebody to take care of all of the 'complexities' and still make a fat profit. I can't pay somebody to take care of setting up and running a software business and make a guaranteed large profit.
That profit is parasitically extracted. No 'work' was done to actually get it - it's merely the privilege that having money gives you.
Some landlords do do the work themselves, which simply means that not all of the income derived from their properties is parasitically extracted - only ~80%.
Instead, they have to deal with the complexities of finding new rental properties and moving on a regular basis in order to keep the rent in check (or just sometimes randomly because their landlord decides to sell up), convincing their landlord to actually do maintenance, put up with the fact that they're not allowed to make any modifications to the property, etc.
That profit is parasitically extracted. No 'work' was done to actually get it - it's merely the privilege that having money gives you.
Some landlords do do the work themselves, which simply means that not all of the income derived from their properties is parasitically extracted - only ~80%.