Well I did just that. The lady felt bad and understood the dilemma. I refunded her a little money even though she didn't want it. I just want to have more success in the future with it.
In your unique situation I seriously can't imagine why you would want to enter such a glamorous hobby of floor finish stripping.
But here some rules of thumbs to go by.
If they can't tell you what product was used run some tests with basic Zep stripper in many areas, if Zep dont work, bail
If they wont take off their MDF base boards and ask you to just be careful, bail
Slate or Flag Stone?, bail
Brick, bail.
Not willing to pay at minimum $4.00 a foot, bail
Anything other than basic water based floor wax, bail