"As for comparability in rents, I don't think it's as difficult as you are implying. Surely, there are houses in your neighborhood which are being rented out?"

I don't think there are very many rentals in my neighborhood. I judge this by the fact that I see the people who live in the houses making improvements - not contractors, but the residents themselves.

In any case, I think it is fair to ask what the financial advantage that landlords have which allows them to charge less than their cost for rent. This is especially pertinent now that the reports are that rents in a number of cities are higher than homeowner costs.