You have your page on the Net. You have it promoted with the search engines , you've placed your ads , and you sit back and wait for the orders to come in. No sign-up fees. We have an unlimited supply. This is a subject of much discussion.
Some people have some strange definitions.
When they send you their response - that IS NOT spam. Someone comes along and collects e-mail address from the newsgroup. That IS spam. You send a request to someone to send you information in an e-mail. They send you this information, and maybe a follow-up or two.