If it is a condo it will be difficult for financing as lenders do not typically lend to someone who controls a considerable amount of a condo building.Tax PIN’s really do not matter, for example I own property with a house and 3 parcels and the 3 parcels have separate tax pins.

They were built in 1948, fully permitted and have separate electric and gas metering and share water and sewer service.

Underwrite very conservatively, make sure to have plenty of cash reserves, don't over leverage, be open and communicate with your investors, and to truly separate yourself from 90%+ of other investors out there when sh*t hits the fan protect their money FIRST to make sure they don't get burned. 

You should have separate bank account(s) for your LLC(s) and their transactions should be handled out of those accounts

We also hold Exchangors funds in a separate and segregated Qualified Trust Accounts.

Are the units separately metered?  

I live in one unit and have tenants in completely separate unit.

Consider a separate LLC for the new property.

My plan is to add another meter and have main and top floor have their separate meter.

Keep your personal funds separated from your business funds.