[logicchains]

The landlord (or whomever he inherited the property from) created enough value to buy the house. This individual would have refrained from consuming some of the value they produced in order to save money for the house, meaning this produced-yet-not-consumed value could be invested, increasing the overall productive capacity of society. The landlord could even have been a low-wage worker themselves, who saved money for years so that they could buy a house and have a more comfortable life, with the rent they're able to charge being an economic reward for the consumption they forwent.

[collyw]

Or more likely they inherited it.