There is a great potential in product funnels as used in mailing lists to earn you money.
But they have to be set up correctly – something most of the advice I’ve gathered from articles on the web don’t do.
Let’s cover some basics. 3-4% of the people you contact (or opt-in) will buy anything you put in front of them – so the bigger your list, the more income you will make.
80% of your total income will come from 20% of your public – more or less. (And this means 64% comes from 4%, 51% comes from .3% – at least on paper.)
As people don’t find things to be of value, they will drop off/opt-out.
With a poor conversion factor, you will probably wind up with 50% or more of your list being that 3-4% and so this will skew your data. High opt-outs, few purchases will give you a steady income – as long as you keep creating new products for these “buy anything” public. You are then in maintain mode for this small niche – and your income is pegged.