Lead pipe, abestos, etc.7. 

If you where going to be able to recreate the orginal layout, you would of been able to do so by the clues left behind by remaining framing, be it the "honey" holes where the toliets once where, the sizes of the holes in the joist would indicate what pipes ran where be it hot and cold supply, toliets, showers and other industry standard tell tale clues. 

Or alternatively go down to the local housing court, walk up to the counter and ask a clerk who a good real estate attorney is.

The 5% down option was a great counter to the self-sustainability test that prevented a lot of people from taking part in the American dream and buying multifamily property. 

Things like leaking pipe under sink, downspout that needs securing, sewer vent pipe out to the attic, missing smoke detectors in a unit, loose material, etc. are all very easy fixes that we would be happy to make for you. 

The kitchen has upgraded quartz counters, SS appliances, and they updated the bathroom as well.

If all water is off in the unit but the dial is spinning you know water is moving through the pipe and going somewhere (usually a toilet).

You are right, many investors overlook the cap ex side of SFH product, when a roof or HVAC can run you $10K+, re-piping $15K+, and even smaller issues like windows and siding in the thousands.

(It is due to a tree that the city grew and will need to be cut down immediately to remediate the problem). (12k for the replacement of pipes and ~5 kfor tree)

Kitchen tile counter and bathroom tile: dirty and moldy.