1 house on 2 lots becomes 2 houses on 1 lot each

[Michael McCartney]

I hope this is the right category to post this question. But near a rental unit I bought an investor has come in and bought two properties next to each other. One property was a vacant lot and the other was a house, he knocked the house down and is now building 5 shotgun houses across the two lots. I think he had to get the lots replatted to allow for this but is this something that he can do by filling out a sheet or does he need to get approval from the city? I just found out he is planning to do the same thing with two more house right next to the other ones. If I am able I would like to fight against him doing it again. I think his main concern is building whatever will get him the most money and then leaving without caring what impact of what he builds will have on the neighborhood.