Ask HN: Cash-flow muses

Timothy "Four-Hour Work Week" Ferriss has a concept he calls a "cash-flow muse". That's a little business that generates some monthly cash without taking up too much of your time. I think the idea is that with a couple of these running, you're pretty much free to do as you please most of the time.

Some desirable attributes of a cash-flow muse:

- You own it.

- The value proposition is simple enough to explain in one sentence.

- High margin: 4x to 50x.

- Easy to automate or outsource the selling, record-keeping, and whatever other businessy stuff is needed.

- Low capital investment.

- Takes no more than about 4 weeks to manufacture the product.

Ferriss often casually mentioned that generating this sort of cash flow is easy to do. It might take a month of real work to set one up, and you'll likely have to market-test a few ideas before you find one that's solid enough to commit to, but once it's up, it should pay your living expenses.

That sounds really good--when talked about abstractly. The main idea is really not that a cash-flow muse can free up your time, it's that cash-flow-muse opportunities are abundant and easy to find. I myself have little concrete idea of what sort of tiny product you could turn into a tiny business like this, and scarcely any idea how to begin searching for one.

My question: Has anyone actually done one of these?