I would highly recommend starting out your soon-to-be smashing success of a business on-the-side as I did. Have yourself a mistress from your full-time job (but just from work, not, like, a real mistress, don't be trashy). Moonlight, work weekends, use any free time you have, even if it's an hour a day, to do your side work.
Many people have asked me how I was able to go from the 9-5 to life as an entrepreneur. Well, first step. I learned how to spell e-n-t-r-e-p-r-e-n-e-u-r. Check! Then, I figured out what I was willing to live with and live without when it comes to lifestyle choices. What is the minimum amount of money you can live on to cover your bills, eat, save a little and enjoy life. Figure out the lowest possible number and then strive to get a few small regular clients/contracts to reach that number. Once you have that in place and can feel comfortable that you can actually sleep at night without stressing, then I say take the plunge. Then, everything else you make on top of that, will be extra. *When figuring out this number, MAKE SURE you account for taxes you will have to pay quarterly. Be sure to over-estimate, so again, anything you over-estimate will have been sitting in a savings account earning a tiny amount of interest.* A great resource to figure out how much you need to live on is at Tim Ferriss's blog. Tim Ferriss is the author of 4-Hour Workweek and 4-Hour Body, two fantastic reads that will get you thinking differently! Check out his monthly expense calculator that will help you figure out exactly how much money you need to live on per day. Breaking it down to the day level makes branching out on your own much less daunting.
So how to find these contracts? Reach out to former employers, volunteer with a charitable organization for a small amount of hours at a discounted rate, ultimately: find a need and fill it. Check Craigslist.org in your area. There are gems hiding in the gigs section for most large metro areas. For my first contract, I had been moonlighting on a freelance basis for many months on the side of my full-time job. The work kept coming along and was challenging and fulfilling. After months of demonstrating my commitment, I simply asked if they would be interested in signing a contract to guarantee hours for both their benefit and for mine. Never underestimate the power of asking, no matter how crazy it may seem! And, even if the answer is no, at least you know you tried and know the definitive answer. Better than wondering, in my opinion.
While you are searching for opportunities, make sure you create a starter website, and starter "brand" to have a place to refer potential clients. I say starter because as soon as you are ready to take the full-on plunge, you no doubt will want to re-brand (as I currently am). But, if you work on it carefully and work something out that you like, or can live with for a year or two, perfect!
I'd say, the most important things to have in place are:
1.) Savings (3-6 months)
2.) All necessary equipment (software, hardware, etc) to do the job you want to do
3.) At least one guaranteed contract of work: enough to cover a basic, reasonable cost of living and taxes
4.) A company name, website and if you are able to ahead of time: a logo, business cards and all social media accounts
5.) A running to do list of what needs to be accomplished quickly once you jump in
6.) Professional affiliations paid for and up-to-date, as well as a few networking events on the calendar
Those are the basics. Could you do more? Absolutely. But, sometimes, it becomes too difficult to work full-time, freelance and actually live with the limited amount of hours every week. While in this stage, though, here is a great resource from Jennifer Blanchard of Procrastinating Writers Blog: the un-schedule.
So, all in all, make sure you make the time to transition. Depending on your current situation, even six months of set-up time will get you into a great position to make your business your full-time endeavor.