I question your definition of SPAM. To me SPAM is not just unsolicited email, but unsolicited email that has no relationship to what you do. How would you define a legitimate sales solicitation?
SPAM is IMO, any unsolicited commercial mass mailing (UCE or Unsolicited Commericial Email). I don't care if it's something I'm interested in or not. (In this case, I don't want it). Check the CAUCE definition if you're not sure.
These mass mailers cost a lot of internet bandwidth and money and are often going to people who have no desire to see them. So much so that we put SPAM filters on and occasionally one or two gets through. There is no business relationship between us nor will there be.
I can't say whether or not his business is legit. I just wouldn't do business with anyone who mass mails like that. Just like I don't like telemarketers and won't buy a thing from them. There are plenty of ways of getting your business out on the net. Take out ads on reputable websites. Get your business mentioned in writers magazines. Market yourself effectively. There are lots of other good ways to attract customers.