His analysis is that roughly 75% of his ownership costs are equivalent to a rent. To be able to invest the other 25% of his cost of ownership into something else, he would have to be able to find an equivalent property that he could rent for 75% of his total cost of ownership (or accept a reduction in the size and/or quality of his home).

I don't know how realistic that is across many different areas, but it's certainly not possible in many locations.