How can I find products/info to sell through opt-in e-mail?

Answer 1

Try visiting

http://www.cj.com
http://www.clickbank.com

also, you can buy stuff through ebay and sell it through opt-in email.

As a matter of fact you can sell just about anything through opt-in email, however, you need to develop your opt-in email list.

That's the key to success - the List.