A character in a favorite book of mine Cryptonomicon by Neil Stephenson at one point talks about fuck you money, in the book he has a spreadsheet that calculates the absolute value of FUM depending on a load of external factors. Essentially FUM is enough to do what you damn well please and to say no to any job offer. Obviously the do what you please part will differ from person to person so of course the amount does as well.
Its never going to be small number, the assumption is that it is enough to replace income as well as doing fun stuff.
Most people spend their whole live saving just to replace their income with the return on their savings. Its called retirement. Hmm, I'm impatient.
In the Four Hour Work Week, Tim Ferris talks at leg about creating a small simple business to generate enough income to support a life of adventure. Its not designed to make millions just enough. The most important thing about it is that from the start it is designed to be automated and give you free time at the same time as income.
Getting to FUM on an hourly rate is always going to be an issue, no matter what your hourly rate.
Just need an idea for something now, there are loads of nice ideas in the book but they seem to have got stuck in my head and blocked my usual creativity.
The general theme i finding a proven product in one market (geographical or demographic) and repurpose it to another. Thats got to be doable hasn't it?