ecm3, not that long ago I was seriously looking into buying a used high-end restaurant grade gas stove. After tons of research it was clear even refurbished ones were potential money pits filled with never-ending aggravation for a home cook. There's a reason restaurants are required to have those huge fans and hoods fitted with a sprinkler system. I'm so glad I resisted the siren song of all those BTU's and getting a $6k stove for $600.
Several of my friends own non-commercial stoves by Wolf, DCS, Viking, et. al. but buying a used one is probably not a good idea either. They tend to be persnikety and costly to fix. New ones are very expensive, costly to fix and depending on the maker, persnickety.
FWIW, we ended up with an induction range which performs just as well as our friends' DCS and Wolf. Super high heat, great lows for stocks and as responsive to temp changes as gas.