A little background before I start asking questions. The building in question is a 4 apartment building, 2 on the first floor and 2 on the second floor. Currently they have 60A service each with the main 60A breaker being on the power companies meter outside with an 8 slot sub panel of sorts for each apartment. Currently these sub panels are in a locked storage room on the wall immediately facing the meter on the outside. As far as the condition of the existing wiring, it is horrible and everything needs to be replaced. There are 30A circuits that are a 3 wire Romex stapled to the siding outside for the air conditioning, an old 2 breaker fuse panel in the bathroom, various wire that is run around studs that are exposed to the living space, outlets and switches that are screwed directly to boards without any electrical boxes behind, etc. I am ripping out most of the latte&plaster to repair damange and put in insulation so wiring the switches and outlets should be easier. Currently each apartment is ran off a single 15A breaker a piece (aside from the AC circuit)

Things I want to do per apartment:
-add 7000W of baseboard heaters, 3500W each on 2 sets of 12AWG 20A 240V circuits
-add a dedicated 20A circuit for the window AC and gas furnace (figure both will never be on at the same time)
-20A circuit for lighting and a fan forced 120V bathroom heater
-20A circuit for outlets
-20A circuit for bathroom and kitchen
-move the sub panel breaker box into each apartment

Questions I have regarding this:
-What are the regulations regarding bathroom and kitchen wiring per breaker(do they each need their own dedicated circuit, etc)
-I commonly hear that you can put 16' of baseboard heater per 20A 240V circuit, using the 80% rule that would add up to 20.7A which is too much. That is one of the reasons I chose to do 14' of heater per 20A circuit. Is the .7A extra ignored normally?
-I would like to move the sub panel breaker boxes to the apartments, 3 of the 4 require moving it no more then 10' but the other requires running the feeder wire through about 20' of living space in another apartment. Is there any problems with this? I was planning on replacing the breaker box with a 60A switch and using conduit with 4AWG feeder wires from the switch to the sub panel.
-I am torn between using PVC and EMT. PVC seems to be easier to work with but a little more expensive (I have done some EMT before and didn't care for it). What is the consensus here? I am running a green in all runs either way, the runs will be along floor and ceiling joists as well as in insulated walls (batt insulation)

Before I get into the detail, are you a licensed electrician ( judging by the questions I would guess not)?

I need to suggest that you check with your local city and state codes to determine if un-licensed people can wire multi-family dwellings. The states I am familiar with will not allow this practice.

You should begin by reviewing the Article 200 of NEC for the kitchen:
NFPA 70: National Electrical Code®

I need to see how your doing the heater calcs.

I get 3500 watts / 240 volts =14.58 amps x 1.25 = 18.225, so one 20 amp 240 volt circuit with #12 wire for each heater.

There is no problem running conduit concealed in an apartment to the new panel.

Either EMT or PVC is fine, which ever you decide you can handle.

The building is caught in a zoning loophole, the city it resides in wants it removed because it is zoned incorrectly and sits on an alley with zero setback. Even though it has 4 addresses and the city knows that it consists of residential apartments they have the building marked as a storage shed. I tried to get it reclassified and re-zoned but because it wouldn't fit into their "plan", it was declined. They won't touch anything on the property (includes a single family house as well) until the apartment building is torn down.

I think I was doing the heater calcs only halfway. I was doing the 80% but not the 125%.

The reason I ask about PVC is I thought I remember reading some restriction about putting it in an insulated wall.

I also have a question about re-wiring the house. It has a brand new 200A panel with 200A service, it is an early 1900's house with the only real electrical draw coming from the dryer and A/C as everything else is natural gas. I will be putting about 15,000-20,000W of baseboard heaters, since most of these will be on the other side of the house how is the best way to run the wiring. Have a 1" EMT tube down the center of the house that has branches for all the heaters or run separate 1/2" tubes. I will be re-doing most of the other wiring since it is the old knob-and-tube style that is in bad disrepair.

Brian, your building may be in a zoning loop hole but that doesn't mean you can do this work without a licensed electrician. TK asked some very valid questions. Try talking with the building department before you go any further.