Convert a mixed used unit to residential room

[Chan K.]

Hello Experience Landlord,

So I bought a mixed used property, 3-plex and 1-commercial space. 

The commercial space used to be a business, and it is closed permanently.

The commercial space has two bathrooms and no kitchen/sink.

Discussion:

- I would like to convert it into a studio (residential unit). So practically, I want to convert one of the bathrooms into a shower, and break the wall between the two bathrooms. I also want to put a stove, refrigerator, and sink in there. So, it will become a complete studio. 

Ideally, I can break the wall, add the sink, and bring in the stove/refrigerator in there. 

My question:

1) Do I need to get a permit from the town or/and notify the town development department?

2) Can I do the above myself or I have to hire a license contractor?

3) Would it be possible for me to do everything without discussing it with the town (pretty much not pulling the permit or discussing this change with the town.. etc)?

I just want to know your thought on this, and to see if anyone had done something like this before.

Thanks ahead of time