Triplex w/ Garage Conversion + ADU = 5 units ==> "Yay or Nay" ?

[Julie Summons]

Question to all MF experts on Pros/Cons on my approach on this investment property.

Recently acquired a fixer triplex (front house 3/2 w/ back duplex 1/1) with a detached 2 car garage. Max use allowed by City = garage conversion + ADU above converted garage. That will make it 5 units. No parking requirements per city since it is close to public transit. Ultimate investment goal is to hold it free and clear and use as retirement income. A potential 3rd floor deck (if city allows) has peekaboo ocean view

Ultimate question: what are the CONs for turning this Triplex to a 5 unit vs 4 unit MF?

eg. so far friends in the Lending industry kept mentioning "cannot refi" if has ADU. and 5 unit considered commercial, etc. Still not sure what the "cons" are there ...