Maybe do a survey and make sure that the houses are on their own property, not encroaching on another lot.Make sure the ground water is not so high that it floods the basement, house.Make sure there are not a bunch of termites in the ground, and eaten up wood in the houses.Make sure the soil is not shifting, depending on where the houses are located, think sink hole.Check water pressure.Sooo, many things it could be physically.Then you have to look at the social things like the houses getting broken into every other day, neighbors from the hood, or even a building inspector going through a divorce:)  Or maybe it is just something simple like the buyer could not get financed since the house is a wreck, only certain financing is available.

A lot of times its just a humid location, or the ground water level is high.

But even if you do, there will still be ground water to contend with.  

We can use one well per 25 persons and eventually add an above ground water tank to create a city type water system. 

I've also seen jobs where cesspools were there and the ground water was too high for perculation and a raised mound was needed $20k+.

The water from rain and snow, as well as ground water, is diverted through the drain tile (its just a pipe system) into the sump crock and pumped out with the sump pump.

You could experiment with the result of turning off that meter valve.Your sump pump should be expelling ground water that has migrated to the basement or crawl space.

If you're in an area that has ground water, such as from close proximity to a spring or river, then you may be looking to add a sump pump too.#2 Properly ventilate the crawl space and finish it with a vapor barrier.

If water is not available, how difficult is it to have a well and what is the ground water quality at various depths? 

You can also call county and pay some postage and they will send you flood maps and flood zones for your hosue- by mail.Of Course--Florida or any one near ocean is lot differnet then in Georgia or Tennessee-- In low lying areas like Florida with high ground waters and no deep creeks or rivers - flood zones every where - Problem is USGS / Army Corps and USGS have not upgraded flood info in 50 years - and there is lot more developments in last 30-50 years - which increases runoffs and chances of flooding goes up every where.