How to confirm amount of legally allowed units in property via online records

[Eric Samuels]

So I'm analyzing a deal in Philly currently and I'm being told by the owner that it's a triplex but I'm only seeing two listed units on Zillow (I can't check the actual MLS since I'm not licensed). I'm of course going to ask the owner if the unit is legally a triplex and I did confirm on atlas.phila.gov that it is RM-1, which is good but wanted to see how I can confirm through online records that it indeed has 3 units and not 2. Would love the help here!

Thanks,