For instance, in one complex I can only charge $1650 because hot water is electric and regular water is the responsibility of the tenant.

Mutifamilies come with a bit more complexity and potentially "unexpected" bills.

I'm looking for complexes that are value add with at least 50% occupancy but not 100 percent vacant.

I started out getting duplexes and SFH a couple of years ago, Last year I made the transition in Multi Family Apartment Complex Acquisitions and now my investment group raises private capital from investors, it's been great and I love working with others to accomplish mutual goalsOh man, we just heard the Greensboro/Raleigh/Durham area is a pretty decent area and the weather is a heck of a lot better than up here in MN!

The same market conditions that affect large apartment complex vacancies will generally also affect 4-plex vacancies in a down market.Advantages of having a fourplex is limiting downside risk and having peace of mind by locking 30-year rates (as some people have mentioned). 2-4 unit buildings also allow cash constrained investors to get in on the RE game, particularly with techniques like house hacking. 

So I bought a 32 unit apartment complex with 10% down.

The complex or units should be able to cover your $40k income and payoff your debt at the same time.

I have done several deals on the flipping side (About 4) , and currently am a partner in 9 units of buy and hold units (1 small apartment complex and 1 SFR).

Could be $10k and up depending on complexity. 

Do not ever think that hiring a PM makes you immune.I have a former client that owned a couple apartment complexes in California for 30+ years.