There are a few that come to mind.
1) CMaxwell is on to something. College professors have a FANTASTIC quality of life. A buddy of mine is a PhD (in physics) and teaches at a university. He is tenured and probably does 30 hrs per week. Tops. No hours per week in the summer. He's not rich, but he certainly isn't poor. The cons to this are an illiquid job market and high student loan debt. I can't bear living more than an hour from the ocean, so an illiquid job market is a big con.
2) I do mostly forensics & litigation consulting. The work is interesting and the rates are good (about $200/hr for staff and $400 to $600/hr for partners/directors), however, there is a risk in that this is the kind of career that can go away in the blink of an eye if you get Dahlbert'ed (legal standard which means removed as an expert). There aren't too many professional compliance costs/considerations (basically just SSVS No. 1 and SSCS No. 1); however, there is a lot of law that you need to stay up on.
3) Sole practitioner (with a decent book of business). At $200/hr you only have to bill 500 hrs to get to $100k per year. That's just south of 10 hrs per week. Granted, this doesn't include marketing and non billable time, but if you spend another 25 hrs per week non billable, you're still pretty much getting off every Friday. All year. Another plus is that you get to directly work with the clients who will personally benefit from the services (families, small business, etc.); whereas with larger clients, CPAs are oftentimes working with employees who could care only enough to keep their jobs.
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