Building cost of 12 units. One big building or duplexes

[Matthew Wright]

I currently have a property with a 4 unit on it. I can build 12 more units. I’m torn between building 6 duplexes or a bigger building instead of multiple duplexes. Has anyone had recent experience in this or recently seen the numbers on which is more cost effective? Also, It can’t be subdivided and the duplexes won’t be able to be sold off individually. All 16 units would have to remain on same lot/deed forever (so in terms of value, I can’t capitalize on the duplexes being sold to conventional non commercial buyer) think financially it would be nice to phase it out one duplex at a time. But seems efficient to go with a 12 unit or 2 six unit buildings. Maybe the construction costs would end up being the same no matter how it’s done, but I haven’t done much new construction last few years, I’ve just been buying existing stuff, so I just don’t know. 
thanks!

[Robert Rixer]

A larger multifamily build would generally be more cost efficient as you have less exterior footage and can combine MEP systems. Being able to phase the duplexes is a nice advantage however. I would say take a deeper dive into the nearby product and see if there is a premium in rents for a duplex unit versus an apartment.