@Michael Schmalzer, I toured the property today and all seem good--HVAC are older but in workable condition, roof is fine, exterior and interior are both in good shape, previous owners have done a great job maintaining it. The NOI is actual numbers provided by the seller, it includes most of the things you mentioned. And I compared the numbers with the comp (expenses were listed on the original MLS), they are in the same ballpark.
I was pretty nervous initially, buying a four-plex as a first deal is absolutely beyond my wildest dreams, so much money involved, kind of crazy...but after analyzing all the numbers and seeing the house in person I feel I am making an informed decision and have less fear now.
Your idea of connecting with other owners is brilliant! I will definitely try that. Thank you for all your help! Really appreciate it.
There is quite a lot of useful information in this thread, thank you everyone who contributed your thoughts. I've learned a ton from your replies.