I have never firewalked, yet 20 years ago I had a neighbor that would hold firewalks in his backyard.  Many people would show up in pretty darn expensive cars, go into his house around 3pm.  At around 12 midnight I would hear jublilant hollers from his backyard.  He would pay off shift firemen to stand around and make sure nothing caught on fire.  The people would then go home around 1am.  It seemed pretty legit and he seemed like a pretty normal person.