Owning a business of my own that requires only 8 or so hours a week of actual work, I get many guys over 50 thinking "I'd love to do this as a retirement project" and as Kimber6 puts it "even if I didnt make squat doing it. Just be an old fart and BS with people all day"
Aside from working instead of complete retirement, I see two real problems with this. First, you'll likely need to risk capital, some more than others. So can you venture that much $ and handle it it fine if you lost it all?
Second, most businesses face a competitive landscape, especially if there is a low barrier to entry (low capital expenditure...say like hairdressing). So in order to do well, you must work very hard at it to get established and eventually make $. This doesn't sound like ER to me.
My business took 2 years of planning, a lot of $ and 1000s of hours of work to get it established to the point of only needing 8hrs a week to maintain. But still I worry.
But if you can make $ with your passion...that's the ticket! The rest is simply exchanging life energy for $ (aka a job).