May Birthdays 
I got my M3 for $35 at a thrift store. I've seen them for a lot less than $325, so I would wait on it or try to talk him down.
You still need to get modifications to get it to have a line out on the amp too, so you should put that into your budget, as well as a leslie or leslie simulator (rotovibe or motion sound, or a real leslie).
My advice is if you are a gigging musician with a low budget, to get a hammond emulator midi module and a midi keyboard (Voce Micro B, Micro BII or Voce V3 or similar). You can get those on ebay. If you are just recording and have a midi keyboard, get the Native Instruments B4 software, it has a VST plugin that will work with any recording software. That's all that I use now for the hammond sound
The M3 is a great sounding instrument (it's the real deal) but you won't be able to take it anywhere with ease, you will need a line out modification (it just has a leslie hookup), and it lacks the leslie simulator.
