So I buy a house built in 1959 that was never updated once and I  spend years of sweat equity in modernizing it and spend countless thousands in doing so and this guy thinks he should tax that?   There's a recipe for decrepit neighbourhoods.   

When landlords run a slim margin (rent just covers cost) you do not see them updating the dwellings and making the neighbourhood better, you see them cutting costs the best they can so they just break even.