IMHO this is a tight high wire act.
If you have already purchased the property without checking then by all means try to see if you can get it ready to rent by:
1) Do not try to get it set up as a duplex!
2) you will need the two meters turned on by the electric service. If this can be done w/o a building permit then step one.
3) you will need water in both units. Check to see if they are together or also separate. If not together but separate then you will need see if you can have both turned on w/o a building permit. if so then you made step two. If they are together then you need to figure how you work with the two rentals to pay the water bill or pay it yourself.
4) You will need to work out how mail is delivered for two parties at one address. There will not be two address numbers. I don't think the PO cares, just your tenants.
If you can do this then you should be under cover and fine unless you have a real aggressive building code enforcement or someone complains about something.
I know of an effort in Savannah to make a duplex like this to code. It is/was a disaster. They were required to meet fire codes on a two story.. new fire "Walls and ceiling" separate HVAC. If you didn't plan for it you will not get there officially.
I would try on the sly. Good luck
Cheers,
Buddy