Hang on, his return on his capital may be the risk-free rate plus risk compensation, but Omid's $1000/month is not the landlord's capital, it's his revenue! Unless you have a good way of mapping rent payments onto the amount of capital tied up in the building, I don't see how your answer is useful.
Revenue from a renter is simply investment income, and we'd expect the income from an apartment-bond to, like any other investment, be squeezed down to equal other investments after adjusting for risk and diversification and taxes etc.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.