Converting a SF home on a MF zoning into Duplex

[Saika Maeda]

Hi all, 

Wanted to pick your brain if you have an experience on this. 

I'm looking at a SF home (4+2 on 1500sqft living space) on a MF zoning to convert into a Duplex (2+1 and 2+1). When doing that, what are the considerations I should watch out for? Do I need to get a permit? The house looks pretty updated, so if the rehab budget is solely for "converting into duplex" (like putting walls), will there be special or extra costs associated with such activity? Just wanted to see if this is something a first-timer can take on. 

Thank you very much for your help in advance!