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.

Also, just and FYI but have you checked that they have all the permits for changing the SFH to a multi?

You may ask, why not wait till you do the entire gut, but my consultants suggest that an interim step of abatement and a temporary rooftop allows for the permitting process to be smoother with a clean asbestos survey.  

Our doing the right thing, contact the zoning department and explain to them what you will want to do and if it will require a special use permit or if it can be done as of right

O&E is Owners and Encumbrances, it provides current information such as the current or last owner, liens and encumbrances of records, any pending litigation, construction permits filed in the past (usually) 6 months, ordinance violations and current taxes as well as other current matters.

@Ram SrinivasanI set out to answer you this morning, but BP suddenly decided I was an unverified user and would not permit me to post ....

The seller had pulled permits back in 2011 to de-convert the basement and do some other items but never paid for the permits or actually done any of the stuff.