Hi Ginger -
if he lives in/near a decent size town, i would recommend craigslist. only after he does research on what it is really worth.
here's a little bit about the machine (not including the cabinet) -
http://www.using-sewing-machines.com/Bernina530.html
there's one on ebay now with 0 bids starting at $50.
not sure if the cabinet would be convertible to other machines? probably best if he priced them together.
just my 2 cents. what area of the country is he in?