some cities/states offer down payment assistance programs.

The main risk is that the city might make you demolish the improvements. 

In my opinion this sounds like a substantial investment, and there are plenty of solid multi-family renters in the following markets:DearbornDearborn Heights Melvindale Westland& other cities immediately North, East, or West, of Detroit You're spot on about renters paying less for a duplex over a SFH but as you progress in the multi-family market you'll notice the differences aren't much if you choose the right property, construction finishes/overhead, tenant screening processes. 

Any advice on CITIES for buying multifamily building for buy and hold purpose?  

I see people post no deals , all deals are dried up, too much competition not like people know all the houses in all cities/neighborhoods in their state.

A flipper friend of mine bought a 3 family near long island city for 800k in 2015, it is now worth 2 million.

I'm an investor w 2 properties in New York,  Hudson Valley, Orange county looking at moderate expansion and investments in single/multi family houses.

Lender - has to be licenced to lend in the state where the property is located in - You will likely get better customer service/lower fees if you go to a small lender in the area where the property is located in.Attorney - Each state/cities' law's are different.

While it is lower today it remains to be one of the highest cities in CA with limited job opportunities.My advise is expect for contingency putting reserves in the right places.

I keep called the city and no response to messages!!!