To answer your question specifically, look for loose or curling shingles, discoloration, particles stripping from the shingles and falling in the gutters (they look like tiny pebbles), streaking, or roof leaks inside (a very late sign). 

I cleaned mine ok with lots of tedious caution and a little flash light, but am hesitant to recommend it as a DIY service to others since it was harder than I imagined and since I believe many AC companies will come do an annual service with coil cleaning for around $150 (again, just guesstimate) and likely have a method more foolproof than my aerosol cleaner can and garden hose, plus they can look the system over and catch/fix any small issues before a home inspector would find them. 

Unbeknownst to you little itty bitty particles has landed on YOUR toilet paper.

Material quality sometimes improves (i.e. drywall vs. lath and plaster) or sometimes gets worse (i.e. particle board vs. solid oak trim). 

What you want to make sure is that there is no particle board in the composition, which is what makes up most laminate flooring. 

You can always use particle board with handles screwed in, like the previous owner did for two duplexes I bought last year. 

If there are particles of food in the sink water, they'll show up in the dishwasher too, and may cause a smell, especially after they sit for a while.If this is happening, the fix can be as simple as making sure the drain hose has that raised loop in it. 

I doubt I could get the cheap particle board stuff for less thank 1K and I would think the better quality would hold up much better and be easier to repair, not to mention maybe help with appraisal come refi time?

The boxes are particle board held together with staples.  

The moisture from the dishwasher steam is causing the particle board to beeakndown.