Yes, good advice, and just a quick thing to add. Most software is sold as a license - you are purchasing the right to use this software. Licensing terms vary as well, some are single machine licenses, some are single person licenses. My guess is that a license can be sold or transferred for most software. I work for a software company (nothing to do with audio), and we have a database of all license holders. Switching owners of a license is fairly simple and doesn't cost too much.
Also, along these lines, the company may be more interested in selling you a new license rather than letting you transfer this old one (they don't get a second sale from a transfer). They may try to "sell" you on the idea of purchasing a new license before letting you transfer. If this person has a hacked copy that they are selling you (or one that a bunch of other people are using already), this may or may not be a bad idea. As you mentioned, companies have different policies for upgrades, updates, support, etc.
smtcharlie