working URL: http://blog.idonethis.com/how-we-got-to-1-000-in-recurring-r...

"By that point, iDoneThis for personal, self-tracking use had grown to some 40,000 members"

Step 1: get 40,000 free members. Step 2: get 333 (0.8%) to sign-up at $3/person/month.