I'm not sure how the builder ever got a legal permit to construct this duplex. 

When time permits you might consider completing your profile.

I talked to my carpenters who helped rehab and they said they could put up a garage for a lot less but I know the problem is I have to do the planning, get a permit,  get the concrete guy, the electrician, ect, but wait-that's what I do when I do a rehab so I took a class on general contracting, took the post class test and scored 96% and take the exam for my General Contracting license next week. 

Looked up permits online, new electric panel, permit on a new roof etc. 

Currently our hvac, electrical and plumber all pull their own permits, if needed.  

Hi Martha, one thing that jumped out at me in reading your question was this: you mentioned the duplex had been added on to--if you haven't already done so, then make sure you have an inspector who is familiar with city code make sure that the additions were built to code and with permits.

Call the zoning office, give them the address and ask if the current 2-family use is permitted or grandfathered in.

Once you get into doing full rehabs you will need to worry about permits and inspections and things can get pretty tricky especially if you are new to the area.

any relevant comment is welcome.What other paper work is needed other than worker comp, permit ?

That being said there are some municipalities that will let you buy a permit to put up a sign, generally on a per sign basis.