underground oil tank on potential purchase

[Michael M.]

Found an investment property where everything looks great and seller accepted offer.  Inspector noted that the heating oil tank is underground in the backyard with concrete over it.  He suggested that I get it tested for leaks as the house is old (1915) and we have no way of telling how old the tank is.   The internet makes it seem like underground oil tanks are the end of the world and immediate deal breakers.  Does anyone here have any experience with this?