Multi's vs Single Family market in Philadelphia

[Joseph Wright]

As an agent that sells primarily single family rehab project in Philly, and spends my time analyzing numbers on returns for flips and rental projects in areas that will return the most favorably. 

I come across countless numbers of investors that are looking "only" for multi families, yet multi-family deals seem to be the most complicated to bring to a closing table. 

The city's "master plan" of zoning being implemented and moving almost all properties into a single family RSA-5 or RSA-3 category, seems to complicate things a bit. 

Scenarios

1.Outdated shell on a block of all mutli's, but the neighborhood has since been re-zoned to single family. This leaves an investor with the choice to take the property as a single family, and possibly fight a battle to get a variance for a duplex approved, which would vary by difficulty typically by neighborhood. Also neighborhood's typically seem more willing to allow a more part time mom and pop investors to get what they want, as opposed to a clear cut "big developer".    

Perfect example: 

My team recently sold an outdated quadplex in West Philly, zoned as RSA-3 (residential design: Duplex). The structure had 4 units, but only 2 in livable condition and occupied. The owner had an expired rental license for 2-4 units. 

:The debate was if you applied for permits to rehab the structure for 4 finished units, the city potentially could force you to add fire sprinklers which are held to very strict standards and higher costs. 

My question is this:

What are some successful multi- buys out there anyone has had experience with?

Duplexes seem to be the most common success, I'm more interested in someone that has pulled off a 3 or more units in areas zoned over to single family. 

Any input appreciated!