Minimum Lot sizes for Duplex/Triplex's in the city

[Mauricio Botero]

Shifting to looking for RM1 zoned properties built as SFH to turn into Duplex or Triplexes. I've spoken with my main contractor about which kind of properties and lots would be ideal. Wondering what our community here believes is an ideal lot size, specifically what I think is the most critical part which is the width of the lot. I haven't built any yet so I have not gone through the process of having drawings done up, but I've been advised stick to lots 15' or wider.

Anyone have any successful full gut rehabs where you turned a SFH into MFH where the lot size was smaller then 15'?