Your point on the 'realisable rent' and the questioning the assumption (will 25 lakhs worth home, can help realise a rent of 13,500) make good sense to me.
And of importance is the Present/Future value of money which should have been taken into account. Probably the author did not want to complicate things much by talking about PV/FV. An excel sheet comprising all calc including the PV/FV would be welcome for the readers to experiment.
