The typica test includes a magnometer (super duper metal detector) as well as looking for signs of a tank (vent or fill pipes, cemented over holes in the foundation wall where the lines came in, etc).

@Wayne Brooks  I don't know about your short sales.. but I know when my wife did a few and one specific I remember was a dentist who wanted to be a flipper  and was upside down about 100k.. the bank made him sign a prom note to release him.. so even though my wife closed the short sale the doc still owed 100k over time. 

I recently looked at a duplex and wanted to get some thoughts on if these items should be factored into the offer price:The water heaters were over 10 years old, both gas furnaces were over 10 years old, the water was not separately metered, the front porch (cement) had some cracks in it, and both units would need some paint and new carpeting. 

Dentist is willing to sign a 10 yr lease and is credit worthy. 

I asked him to check the drain and he said there was no evidence of the drain being touched and he couldn't even remove it (possibly cemented in he said) and according to the tenant "No work had been done they just took pictures of the carper".What leg do I have to stand on in firing them?

It's originally a 3 bed 1.5 bath 1 kitchen 1 car garage but the previous owner put a fourth room in the basement also finished the basement along with another kitchen down there so 2 kitchens, plus new roof, windows and cement within the last 2 years. i know this because i knew the guy personally.

I have gotten a couple quotes and average price is $200 for setting the traps, $60-$80 per animal that is removed and $100 to fill holes with cement! 

My biggest or most unusual problems were: abandoned vehicles, a person escaped from a mental institution, tenants with pet rattlesnakes that escaped their container, a round trip visit to the dentist for a wisdom tooth removal, a one way bus ticket from Kansas to Georgia, cashing $25,000 worth of checks each week for a group of guys from out of state, etc.  

Imagine you are a Medical Doctor, a Dentist, etc.

Also, she threaten to put cement down the drains and to burn the place down.