Those were a drain pan issue and a nonworking exterior heat pump that was causing a circuit breaker trip. 

Could be cosmetic, could be a deal-breaker.

I'd just ground out all the circuits with arc faults or GFCI's at the start of the circuit4 Since I have to get into the walls to do plumbing, electrical, heating, should I assume that the house has to be gutted to studs?

Also some heating ducts will have asbestos. 8x8 tiles are almost always asbestosFor electric you have to put in breakers, no fuses.

Not a deal breaker, but possibly a reason to lower the price that decommissioning amount.

Galvanized pipes will need replacement, as well as all of the valves.It's not a deal breaker if you know these expenses will need to be considered.

====================So what I see is that as long as the occupancy of the FHA-financed property is primary, the existence of other investment properties should not be a deal-breaker.

If it’s a flip, I could reason the cost.If the entire house is 103V, its an internally shorted main breaker (cheap), an issue on the power companies end (free), or a shorted common from the weather-head to the main (not rewiring the whole house).

Put one of those circuit tester things in all the GFCI outlets. 

Because of that and that we would like to store our tools there when we move in -- we would like to limit access -- though we are okay with the seasonal tires.Unit 1 is the only unit whose circuit breaker is in the basement and therefore require access by law.