Mold is caused by moisture, so if you get rid of the moisture your problem is solved.  

The walls will be dense-packed with cellulose, which is a great buffer for moisture, but thicker walls can be slower to dry out than normal walls. 

Exterior measures were taken about 20 years ago and the moisture issue comes and goes.. literally years can occur between.

Below are some generalizations about ongoing maintenance costs: Older properties require more maintenance than newer properties.Composition roofs require more maintenance than tile roofs.Properties in climates with hard freezes require more maintenance than properties in milder climates.Properties in locations with a lot of moisture require more maintenance than properties in dryer climates.Wood siding requires more maintenance than aluminum or stucco siding.Properties with lush vegetation require more maintenance than properties with little or no vegetation.Below is a typical Las Vegas single family class A home.In summary, I believe Las Vegas is not only a good place to invest today, it has a high probability of continuing to be a good investment location into the foreseeable future.

Recommend sloping grading away from home 1" per foot to avoid grading erosion, foundation seepage and possible foundation movement (85-90% of all foundation moisture problems can be avoided with proper grading and downspout extensions).

I believe you usually staple moisture barrier to the studs before the cement board and tile.

That entire part of the country is unstable because of the clay type and moisture expansion and contraction cycles.

The downside is that they can often have excess moisture & are usually seen as gross when you are looking at homes built 40+ years ago.

The subsequent mold WOULD then be your responsibility to resolve because you did not alert the landlord of the condition of moisture, which, when left unresolved, leads to other bigger things like mold. 

In other words, the cost of preparing the area, breaking tiles, cutting open the slab, excavation to the pipe, backfilling with clean fill, termite pesticide application, moisture barrier, rebar epoxy to old slab, pour new slab, new tiles are all covered, the $150 to fix the actual leaking pipe was not covered.I had a collapsed fitting under the house confirmed by camera.