I was a national account manager, as well, with a 90 minute commute into NYC every day. I loved my job but the commute burnt me out and in my industry, even though it was sales, the expectation was that I'd be in the office A LOT so I didn't have that much flexibility. I ended up banking my bonus and starting my own consulting company. I used to work for a very large, well known corporation. Now I consult with much smaller companies in my field (book publishing) and serve as a sales and marketing director. I set sales targets for rep groups, set budgets, create catalogs and marketing materials, and step in and troubleshoot with accounts when necessary since I still have those relationships. (Actually, keeping them up to date is the most important thing.)
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Once I decided to go out on my own, I started to put the word out on the "down-low" that I was interested in consulting, did people know any smaller companies, start-ups, etc that I could talk to? I also talked to other people in my industry who consulted and that's how I got my first job--helping another consultant who had a big job and was interested in some specific industry experience that I had. It all came just from picking up the phone and talking to people. I did a business plan, too.
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It's been three years now, and last year I made more money than I did when working in the city. I work from home 95% of the time, go into NYC once or twice per month, and travel for sales conferences or trade shows every 2-3 months.  I work 30 hours per week, and that gives me time to take my daughter to ballet once per week, and when she was still in daycare, it gave me a really livable schedule (9-3 for her, as opposed to 7am to 6:30pm). Now's she's in kindergarten and I still appreciate the flexibility. I volunteer in her library every other week at lunch time, and yesterday I popped over to school for an activity that I couldn't have done with my old job and schedule. Things worked out better for me than I ever would have imagined--I thought I would give it a whirl for a year and try to keep my hand in the business, but instead this really took off.
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The key for me was going from the biggest and best company and bringing that knowledge of best practices to smaller companies or companies that are launching. I also ended up working with rep groups that represent those smaller companies, and they ended up being a great source of new business. I think being in sales is a big advantage as you really need to sell yourself first!  Feel free to pm me if you have any specific questions.