If the conditions that encourage mold to breed exist (moisture mostly) then it will come back.

Fix any moisture leaks, pest control problems, rotting.

Fix any moisture/vent problems2.

Hey @Scott Peters -Dry rot is caused by a moisture/water problem ... we see it a lot around sinks and bathtubs/showers. 

Looking at pictures won't tell you if the HVAC works (or how old it is), won't tell you if the water heater is installed correctly (unless the listing includes pictures of the water heater), won't tell you if there are leaks under the sinks, won't tell you if there is evidence of moisture in the basement, won't tell you if there is mold in the attic, etc. 

When moisture is evaporating up though the slab and ultimately through your grout joints you'll get water soluble minerals that are left behind on the surface of the grout, its called "efflorescence", and yes, its very hard to clean.The only ways to avoid this is to check the subfloor with a moisture meter to be sure it's completely dry or installing a vapor barrier over the slab prior to tile. 

There are a few tricky details that the contractor HAS to get correct to make sure moisture does not become a problem:1) If used for a roof, make sure the roof is built with a cold roof to allow for ventillation.

So the flooring will need to be completely replaced, but the real issue is moisture causing the wood to swell and "pop loose".The left hand wall where the baths are has a higher moisture content along the baseboard, and the wall between the 2 baths also had a high moisture content.

These houses are still settling and the engineered works better.LVT for the basement areas due to the moisture issues that can occur.Carpeting the steps from first floor to second does help with noise reduction.

Also, wind-driven rain is pushed through the gaps causing moisture to penetrate "the envelope".McVey offers a "lifetime" warranty, but I still have to pay for the labor to pull the oak interior trim, exterior trim, cut the calking out, pull the nails, drop the old window out and put the replacement in, and trim everything back up.