In the past it could be the curse of death, but not anymore! As a contractor I have these issues all of the time and I'm located in Los Angeles where the City departments and pan handlers with their hands out for money, fines, fee's and bribes.
In the last unit I worked on for a client they converted a garage and laundry room into a 2 bedroom unit with kitchen, bathroom and den area.
First I had to confirm the structure was sound, it wasn't. They didn't install the right headers over windows and doors. Had to open up the drywall and make those corrections.
Second, they had shared electrical. I had to install a new panel with meter socket and rewire the unit to code. Making the panel hole 150% or more of the units possible load.
Third the heating, water heater and stove used a shared gas meter. I had to split that and install a new meter.
Forth, the plumbing wasn't correct. Using a number system assigned to fixture units, the water line to that area was under sized. I had to run a larger water line.
I had to open up walls, 12" x 12" to show correct wiring, straps, pipes, etc.
Then I had to blow in insulation, because there wasn't any.
Then the inspector came and wanted more. I know, they always do. He wanted a exhaust fan in the bathroom even though there was a window and a hood the vented outside. The kitchen was in the middle of the unit so I had to build a soffit and vent through another area to the outside.
Then I got the permit signed and an updated certificate of occupancy. I added the unit to the City's rent control list and all was good.
I also had to provide extra parking for the new unit. --47.155.xx.xxx