A single operated newsletter may be the easiest business ventures to set up:
1) Create an account
2) Import your email list (Paidletter shows you how to grow one)
3) Connect to a payment system (we prefer Stripe) to receive payments.
Readers subscribe monthly or annually, and most publications offer a discount for the annual subscription.
5ish is a site and newsletter by M.G. Siegler that aims to serve up five or so links and thoughts a week. In a way, 5ish is a counterpart to 500ish, the site where M.G. Siegler does the majority of his writing, with an aim towards five hundred or so words in length per piece.