Some of the basic models are fair priced such as these:http://shop.watermeters.com/DLJSJ75C-Compact-3-4-w...www.teksupply.com/contractor/supplies/ProductDispl...The most advanced system I came across blew me away!!

Because the soil is so hard and compact from the lack of rain, it can't absorb the rain when it comes down that fast so it just runs off.In looking at the neighborhood topo, I was concerned that the SE corner would get a great deal of that run-off.

I think if I owned the place I would finish out the garage/shop as a compact 2/1, rent that out long term, and then rent the larger house (a 2/3) as a vacation rental, or maybe the other way around. 

This was from the base under it not being compacted properly on the street side and, as the underlying base settled and compacted, it allowed the sidewalk to drop +2" with it, making a wicked trip hazard between it and the curb.

@Dawn Anastasi I love the term 'headache value' as a metric for analyzing rental properties and wish to state this hypothesis : The headache value of a property is directly proportional to the  ROI'.  

Nevertheless, I would hate to be looking for motivated Sellers of Real Estate @ say 70% FMV in areas where even the princely sum of $250k cash couldn't buy any (and/or where Lenders couldn't readily be found to fund just 50% of the sale price, but where the actual loan proportion of the value was less than 30%)!...

There are a couple of potential sources for this problem bit I would place my bet on poor compaction of the subsoil before the slab was poured.

Probably needs good compaction before replacing the slab.

I'm not suggesting the tenant is lying 100%; however, from what I have heard (admittedly very little) I get the impression this tenant may exaggerate things or blow things out of proportion to what he perceives is his benefit.

My experience has been the value of the course is inversely proportional to the price.