So to figure out the overall value of the investment, you'd need to add up not just all the money it's going to cost the owner, but also subtract all the money

So to figure out the overall value of the investment, you'd need to add up not just all the money it's going to cost the owner, but also subtract all the money the the owner did not have to pay in rent. I'm countering this assertion that you need to subtract all the money that the owner did not have to pay in rent because this is going to be equal to the amount that the owner did not earn in rent by renting out their house. People who buy a house for living (rather than rental) do not often make a rational economic investment decision which is kind of my point. Sorry, I did not make it clear that I was assuming a comparison between renting and owning in the same neighbourhood. People (Americans in particular) generally rent apartments and buy houses, as you rightly pointed out. Within the same neighbourhood, a house is going to cost more to rent than an apartment.