If the tanks are: big enough, owned and not leased, and not in need of hydrotesting, and the rest of the equipment is one of the big 3, being: Victor, Harris, and Smith, it might be a good deal. See what he has, see if parts are still available, and search the internet. I will usually pull the trigger around 50% of the cheapest price available on retail pricing.
I purchased oxy / propane two weeks ago and one of the gauges were bad. I ordered Smith gauges for around $80. Still came out pretty good