In France we benefit from a system called "Entreprenarial Vacation" - anyone who spent 5 years in their company can ask to take a year off in order to start their own business. The company can accept or refuse. After 12 months, the employee can decide to leave the company for good (business works) or return to his former functions and keep his job/salary (business doesn't work, founder is not fit, crisis in the world- you name it).

I oversimplified it a bit of course, but basically you should check out if there are any system like this one in your country. I personally took this chance and I am freelance right now under these terms. I already had a contract ready to execute when I started, which helped tons.

Just one thing: expect up to 3 months delays in payments and expect administrative delays (at least three weeks, for me it was two months- don't ask) from the moment you have a bank backing you up until you can issue your first invoice: that's what it takes to incorporate a company. So worst case scenario is even if you start with a gig right away, you might have to eat all your saved up cash before seeing any money income.

Looking back at how it went for me, I would have rather started working on all the administrative details before leaving my previous company. Then again I'm talking about the French administration, I don't know the specifics in other countries.