Permits

T2,
Permits are required based on the type of work being done,regardless of the size of the building or what it is used for; i.e. residential,commercial,warehouse,church,etc.

So I want to put in new wiring, run some new pipes and install flooring (all of which I am capable of doing), do I need a license? I thought for some reason that this is permitted for 1 families.

T2;
Wood flooring you can do without permit.
My understanding is that for electrical and plumbing,on a single-family house that you own,you are allowed to do the work,but it must be filed and inspected,the same way it would be if you hired a licensed tradesman.For bldgs. of 3 or more units,there is no exemption,as far as I know,but regardless,you should check Dept. of Bldgs. website.

can i do the work on a 2 family. inspections are useful but i don't want to be paying someone for something i can do.

The reality is, you can do whatever you wish to do and not have a problem, as long as the neighbors/tenants don't call 311 and you don't ever have the need for an insurance claim.Decide on that gamble and you will know how to proceed.

I want to be on the up and up which is why i am want to verify laws. I don't need the stress/risk of trying to do things on the DL

Then as I wrote in my first post,you should file the job and have your work inspected,even though you will be paying for services that you feel are unnecessary.That is how one sleeps best at night in many aspects of life,especially if there is something at stake.Pay your fair share of taxes,don't intimidate pedestrians in x-walks with your vehicle,use licensed professionals when required,etc, etc.