Most small business owners start out in salaried employment and then pursue an idea or opportunity that arises. As a result, there can be a fast transition from a steady income which regularly pays the bills to a cash dependent business with no returns to the owner.
If you have employment, explore the options of starting your business in your spare time, or reducing your employment hours to part time. The regular income will make the transition to self employed a lot easier.
For professional people contracting or lecturing can be a good way to supplement income while building your business.
Before you make the move, work out what needs to be spent and where the money will come from. Consider your spouse's income, your personal assets and access to borrowed funds. In the first few years it will be difficult to borrow from a bank and often home equity or relatives become the sources of finance.
Business Guide - Top 10 tips for a new business