You will need to make sure that there is two completely different plumbing systems.

The other systems that are expensive to replace might be areas of concern; mainly the furnace, plumbing, roof, and electrical.

Older buildings do a full plumbing scope to look for rotted galvanized pipe.

Basically everything is new; roof, siding, windows, electric, plumbing, HVAC, kitchens, bath, flooring etc.

New plumbing, electrical, everything down to the studs.

It's a townhome and everything structural, including foundation/roof/walls and all common plumbing and electric are covered by the Strata (like an HOA) insurance.

Even now I would much rather fix drywall damage myself than get gouged paying somebody to show up three times to perform the repair.I mainly only hire out the things I don't know how to do/don't want to do (roofing, plumbing, electric). 

Very often the wiring, plumbing and heating is mixed between multiple units.

I can do simple things like paint, some electrical, some plumbing ... regular home maintenance stuff. 

If it's something small (i.e. plumbing leak) we don't bother unless specifically requested.