I can't bill him $1,000 because I kept him out of court on a fair housing claim and I can't bill him an exact dollar amount for my skills of being able to keep a tenant happy and paying month after month year after year.

If you're a lender and your homeowner has stop paying, you must file suit in the court.

Now how that all actually plays out with insurance, attorneys and courts in individual cases, and at what costs in money and time, that's the rub.There is usually an insurance policy on the tank, to cover leaks, as part of the price of the fuel, so check with the seller on that.I would certainly recommend making your deal contingent on a clean leak test (and decommissioning if that's what you choose) and have your deal effectively read such that if the test comes back with water in the tank, ie the tank has leaked, then you can walk from the deal and get your EM back.The existence of a UST, especially if in use and not leaking, in no way needs to be a required deal killer though. 

it must be an awful lot for her to get a lawyer and waste a day in court?  

This also helps you if God for bid one of these tenant/buyers decides to take you to court.  

Landlord lived at the property for over a decade and never had such a situation. 2) A/C likely not functioning.

If you are buying for future appreciation, you cannot use the same matrix as you might use if you are buying for cash flow right now, and its usually the function of neighborhood that you choose.Just because you can cash out for "x" amount from a given property, doesn't mean you have to.

Over  a hold period as the asset gets older the operating costs usually start going up more.A seller owning a brand new built asset years 1 to 10 and claiming XX costs might be true but you owning for the next years 11 to 20 etc. the cost profile of the property will be way different as many items will reach the end of their life expectancy and need replacement or multiple repairs to keep functioning optimally.Even on larger multifamily 50% is common for total expenses and if landlord pays utility it can even be more like 60% operating costs.

Just back from bidding at the court house steps and its getting crazy there as well.Good Investing.

Matthew B.Florida courts have ruled making single member LLC's a disregarded entity in many legal proceedings.