Most building codes (IBC, UBC) will not allow this concept without applicable fire codes (state, county, city)being adhered to such as fire walls and seperate utlilities. Should there be only 1 poc for all utlilities you must perform load calucations under the NEC as each families area as being a seperate residence (IMHO).
The only place I see as a problem is a possible lack of load diversity. You still count all of the small appliance circuits and laundry circuits at 1500va each. You might want to count all the stoves as the "first one". The other thing is the general lighting load. It would probably be overkill to put 3va on the whole 6000 feet but it is the safe call. Fixed in place equipment is the same. If it was close, you could probably round down to the next standard service size, assuming you took everything above on the high side. Residential load calcs are just an educated guess anyway. You can have identical houses and one can routinely have twice the electric bill of his neighbor, simply ny lifestyle. Six families shacking up in a 6k ft house are probably on the cheap side anyway ;-)
