We build our duplexes at top quality and abide with proper firewalls and all the necessities for safety but its pretty simple requirements when dealing with 2-family.

Sometimes you may need to build furr-downs to house extra HVAC conduit if you have tight design constraints.3) If you are building a duplex, this is where you want to ensure you can build a proper firewall and sound proofing between units.4) Check your window heights and kitchen cabinet elevations that you are going to be able to hit the plan.5) If you have big open ceilings, make sure you have enough support to hold them up. 

House hack this property for a minimum of 1 year to satisfy VA loan requirement.Rental income from the the 3 bedrooms: ~$2,250 ($750/room includes all utilities; potential for an extra $25 for a garage spot)While house hacking, save up a down payment to purchase a similar property using an FHA loan.ExpensesMortgage: ~2,400Utilities: ~150CapEx: 100 (Roof was done in 2012, water heater may last a few more years and is covered by warranty for first 13 months)Maintenance: 100Total: 2,750Current expenses from renting: ~1500Out of pocket: 500 (equaling 1000 saved per month)Home Inspection Call Outs-Main electrical panel does not have main disconnect (national violation) + exposed wiring in garage-Non fire rated plumbing going through garage firewall for laundry hook ups-Flat spot on roof that shows signs of standing water-Entry way is a trip hazard (hard to explain but will post picture below)-Possible rodent infestation in attic-Windows in 2 bedrooms violate fire egress code (sill is 4 feet high)-Closet doors in 2 bedrooms are oversized preventing full access (again hard to explain but will post picture below)-Backyard sliding door doesn't lock-1 bathroom shower diverter valve doesn't work (pretty cheap fix)-Attic insulation insufficientRepairs/Changes right away that I feel are necessary to make rent ready-Electrical Panel and exposed wiring-Closet Doors-Backyard sliding door-Rodents-Shared bathroom vanity to allow storage (currently a pedestal sink)-Master bathroom shower (for personal comfort.

When her unexpected new boyfriend moved in, didn't pay rent, used her money so she became even more chronically late than usual, invited his friends over to repair cars in the driveway, and smoked in the apartment - all violations of the lease - I regretted letting myself get into this situation.If at all possible put a firewall between you and prospective tenants with a property management company.

But I've also been down to COH and discovered there's a catch: the "4-plex --> duplex" plan above would require us to completely replace the shared wall between the two dwellings with a firewall.

This is an ice maker box which is currently nailed to a firewall (which the drywall I think was partially glued to originally - I don't see any screw holes into the firewall at least from where the drywall sat over it).Is replacing the ice maker valve box something I should consider having a go at myself? 

I was required to put in a 1 hr. firewall (from attic to basement) and have had to open up all walls to reveal the plumbing so any drains etc. not up to code can be corrected.  

If you need 2 layers for a fire wall then use the diagram above. 

I dont think you would be able to put in a water meter and sell them individually.It would probably NOT be allowed to move from one to the other because of firewalls, meters, deed restrictions and also zoning.

In a condo situation, I think it would depend on the closeness of the units, like is it an end-unit townhouse style with a firewall in between, or more apartment style with others above and below?