I was not blaming the people selling the house, I was blaming the banks for putting an arbitrary down payment on getting a mortgage to keep poor people out of home ownership, which benefits the banks as they are all heavily involved in property investment so benefit from more people renting either by directly being the landlords or simply from the increased housing demand from landlords wanting to buy as many properties as possible, thus driving up housing prices, which drives up mortgages and makes them more money.

Like you say, the banks male their money from interest on the loan, so the 20k down-payment they require is an arbitrary barrier to entry.

No, I get it, you're just making up a scenario that doesn't really happen. Like sure a landlord could in theory pay half the price of a house just to reduce mortgage costs so they can rent it out at half the market rate AND pay property tax and maintenance out of pocket, out of thr kindness of their golden hearts. They could also just buy the house outright and let you live in it for free and just make their profit off of the increase in house value. But obviously they won't. The landlord is going to charge you market rate for that 600k house which will almost certainly be more than 3k, because why wouldnt they? And even if they did, are the going to rent directly to you? Or are they going to advertise it and get a slew of offers of people wanting to live in a house for half price and so someone a little bit richer than you will offer them, say 1,750 for the house, because of supply and demand. And the vast majority of people aren't trying to live in houses they can't afford, they are just trying to live.

And even then, it's still not ethical, you're still exploring people for profit for their basic needs without adding any value to the system.