Different keyword rich pages, different subjects, and all linked to your main site home page. Providing direct links in your newsletter to the latest buy and sell opportunities on your site will generate sales. Deliver promptly as promised. Deliver your newsletter professionally and consistently. If you change the day of publication, notify your readers.
Most publishers do have day jobs, and sometimes can get behind schedule.
If you explain your circumstances to your readers, they will understand. Keep current with your mailing list. Add new subscribers on a timely basis. Remove unsubscribe requests right away. Speak to both HTML and text audiences.