Despite a long period with no ventilation, and intentional holes in the drywall to expose the inside of the affected areas, neither my wife or I could detect the rotten egg odor.

For example, why would they come here, how would we detect them, how we could fight them, etc.

After a few calls made, GV detected that the activity was coming from overseas, so the connection was blocked.

Often it takes detective work and calling friends neighbors or relatives from the skip trace report to find who you are looking for. 

I have a client in an urban area that has a detective she calls on every property she is considering buying and gets useful feedback like "nothing wrong with your property but last year there was a shooting in the front yard next door."   

You are not detecting the expenses, taxes and the mortgage payment.

However, the meter is set to full detection in the guru mode.So, the mention of "software" is that the software of public records or proprietary software for wholesaling?

In MD a seller must disclose "Latent defects" In other words defects that are not easily detectable by a thorough visual inspection.

Second if there is a drastic change in the water bill i can look back over the history and compare to similar occupancy statuses to determine if there is a problem with the water that we have been unable to detect(ex. leak in the main water line coming to the house from the street(which you would have to pay for)).This is what I have learned so far in my limited experience.

@Stephen Chittenden Good detective work my man!