Zoning violations - Multiple units in R5 zoned house, how common?

[Jonah Geil]

Hi - NEWBIE ALERT!

We're first-time investment property buyers. We're looking at buying a house that has been running as 3 units for many years. However, it's zoned R5 for a single dwelling. I'm aware that code violations with the city are a complaint-driven system, and the city won't necessarily just drive by and give us a code violation - it usually comes from neighbors.

First question - how common is this?? I understand there are plenty of owners who will turn a single-fam dwelling into 2 or more units without the proper permits or zoning since that is expensive and raises taxes. Should I not worry too much about it?

My worry is that I find it hard to sell the property down the road, or that I do get a code violation at some point. Also seems like because of the illegal units that it would be hard to do anything else (like add an ADU) in the future development-wise without getting a code violation for previous stuff.

Thoughts? Thanks in advance!