The giant midget: It truly depends on what business you want to venture into and the amount of experience / skills you have to put in that business.
1 have about 90% of cash flow of your own to purchase equipment etc
2 have a good 70% of knowledge / experience to operate equipment etc.
3 the more tasks you perform by yourself the less expenses you have.
4 never stop promoting and marketing your business.not yourself
5 have enough cash flow to sustain the business and your living cost for 6 months.
6 never,never,never ever hire family and friends
7 personal hygiene and grooming to the highest levels.
peifo: First, make sure there is a market for your product or service. You place a free ad online and see anyone responds.
Second, don't quit your current job until and unless you make enough from your business to support yourself. That's all you need.