Fairly early on he states that where rents are typically 3% of house prices and interest is typically 4% of a house price "it costs more to borrow the money as it does to borrow the house". Except that interest is 4% of the house price in $YEAR_PURCHASED per annum, and the rental rate is 3% of the house's value in $CURRENT_YEAR per annum so the comparison isn't very meaningful except in the short term: the mortgage payment is a fixed cost whereas the rental rate is a variable that will tend to rise over the course of a 25 year mortgage unless there's something very strange going on with the regional housing market or US inflation and economic growth. Even at modest rates of inflation the total cost of interest paid over the course of a mortgage will tend to be lower than the total cost of renting over the same period (even without accounting for nominal appreciation in house values); whether the additional cost of renting is a reasonable premium for not incurring the risks of owning that home is another matter