What kind of wiring to add light switches in condo
It's quite likely that being in a multi-unit structure like that, you'll need to work to commercial standards in conduit.  Ask when you pull the permit to do the work.  

The multi-conductor rule also applies to conduit.   

The rule has to do with current loops.  All the current going down one cable or conduit must come back in that same cable or conduit.   If you sum up all the current in all the wires in a cable, counting the return (neutral) current as a negative number, this must always sum to zero.   This is so magnetic fields will cancel each other out. 

So for instance you go from 


Cable 0A: always-hot and neutral from power supply
Switch Box A:  switches a hot. Neutral passes through. 
Cable AB: always-hot, neutral and switched-hot
Lamp fixture B: uses switched-hot and neutral for the lamp. 
Cable BC: always-hot and neutral
Receptacle C: Uses always-hot and neutral.  


Suppose you have a 10 amp heater in receptacle C and a 1 amp light in lamp fixture B.   Obviously in Cable BC, currents are equal at 10A hot and -10A return.  However in Cable AB, always-hot carries 10A, switched-hot carries 1A, and neutral carries -11A.  So even though several wires are in play, currents are equal.  

If all you had was 14/2 cable, and you needed to make the connection from A to B, you would run two cables.  It would be wrong to use the same neutral wire for both hots in that case since they are in different cables.  You would use one hot and its partner neutral for the lamp, and the other pair for the receptacle.  

Occasionally you have to think these things through is all.