Do you have a photo?
If the machine is in good cosmetic condition and good working condition, if the cabinet is in good condition and the stool is a matching stool for the cabinet (usually this kind has a lifting seat for storage), it could be a good buy.
You would want to make sure that the bobbin case is in the machine and that the machine actually forms stitches (otherwise it could be out-of-time and need a trip to the mechanic's hospital). It would also help if there are attachments.
301s used to sell for about $300 where I am -- just the portable machine head, not with a cabinet. However, prices have dropped a lot since the economy collapsed. Recently several people posted that they have purchased nice 301s off eBay for under $100 including shipping (although some required additional money for parts).
Overall, I would say that if the machine and cabinet look good and if the machine forms a stitch, it would be a decent price.
The 301 is a really nice vintage machine to have.