You do not need a variance from the City of Jersey City to convert a 3 family into a 2 family. The kind of work you are looking to do doesn't sound like it requires Union labor. The unions are involved on mostly large scale new construction. If you do use a contractor, I recommend using a licensed one.
You could have friends and family help you do with the work, however if you do not have a permit, you risk the City finding out and perhaps issuing a "Stop Work Order" and a fine. If the City sees a lot of debris being left for the garbage collection, they may stop by and ask where your permit is.
Before you do anything I recommend speaking with a general contractor in the area. They would be able to give you an estimate of the cost and if a permit is necessary for the kind of work you are looking to do. You may want to get multiple estimates and opinions.
I'm sure you can find some contractors on this site or ask friends for a great recommendation. They always work the best. I have contractors too that I can recommend if you are interested.
Walter J. Burns
1 Newark St.
Hoboken, NJ 07030
201-653-8488 Ext: 230
I am sure you can convert the building to a two family.. or convert the apartment to use as a two family.
You should call the township construction dept and ask questions.. I am sure there are permits necessary in order to make this happen. All in all it is "doable".