First thing I suggest is that you refrain from indulging in any unrealistic expectation. Unless you have many years under your belt as a successful trader, you might just want to hang on to your job until you learn the ropes. While you might be jobless, the market will always be there for ya. Also how much are you currently bringing home from your 9-5 gig? When you first start trading, use that as the baseline for your profit. Suppose you make $100,000 annually. That would be $8,333 per month or $378 per day (divided by 22 trading days). You would need to make this much to break even. Is it difficult to make $378 on any given day? Possibly. If you were trading 1 contract of S&P 500 eMini (ES), that would be roughly 8 points. Is it impossible? Hardly.
Ironically while I was making all my preparations the decision was made for me. A large number of people (including me) was laid off. My wish has been granted and now I am free to swim in this wonderful market. So far things are going good on the daily front, but my long term portfolio is obviously taking a beating.
Don Quixote comes to mind here. And the proficient trader can also go bankrupt as easily, or even more easily. A crash does not give someone retirement, otherwise the billion dollar institutions would have expanded 10 times in size due to the crash, with their much fore formidable research and financial resources, than Joe Sixpack Trader at home, with his 3 monitors.
I am in the process of doing the very same thing. I have a lame comfort job, it sucks up a lot of my trading time but oh well. Honestly, if you want to trade full time, do it responsibly. Trade part time, or take a week / month off. If you are profitable you can consider the jump. It would be ideal to find a trading system and "comfort" job that allow you to do both. I am trading part time until I get cocky.