If the duplex is making money comfortably and you don't see any red flags (neighborhood going downhill, area losing jobs or population, etc) I would keep it and grow your portfolio by whatever means makes sense

Everyone evicted: who ever picked six bad apples was incompetent and the subject is in the red on the crime map.

stay away from flood zones

@Rayan PerezHere are my favorite books:Multifamily Millions by Dave LindahlThe ABCs of Real Estate Investing by Ken McElroyThe Complete Guide to Buying and Selling Apartment Buildings by Steve BergesCommercial Real Estate Investing by Dolf De RoosTrump: The Best Real Estate Advice I Ever Received by Donald TrumpTax Free Wealth by Tom WheelwrightCommercial Real Estate 101: How Small Investors Can Get Started and Make It Big by David LindahlRaising Private Capital: Building Your Real Estate Empire Using Other People’s Money by Matt FairclothThe Definitive Guide to Apartment Marketing by Josh GrilloInvesting in Apartment Building by Matthew MartinezCrushing It in Apartments and Commercial Real Estate by Brian H MurrayThe 7 Secrets to Successful Apartment Leasing by Eric Cumley2 Years to a Million in Real Estate by Matthew MartinezBurn Zones: Playing Life’s Bad Hands by Jorge NewberyCommercial Mortgages 101: Everything You Need to Know to Create a Winning Loan Request by Michael ReinhardIt’s a Whole New Business!

Beyond that, I usually let the general inspector call out any red flags and if he/she recommends an HVAC inspection, we can make some recommendations; those are usually ~200-250.lastly, you'll see a lot of boiler heating. 

Utilities, park owned homes, zoning, etc are some of the things to look at.

Definitely look out for flood zones.

Have you looked into opportunity zone funds or syndications that provide bonus depreciation?

Is this a red flag?

He also advised to work with my CPA to make sure I’ not too far into the red.