If you plan on quitting your job, don't just follow what people comment here. The actual amount you need should be calculated yourself, based on your plans.

1) How much money do you need to get round per month.

2) Add a chunk ontop of that for unforseen expenses, broken fridge for example...

3) How long do you estimate you'll be working on your project?

4) Add a large percentage to that estimate for unexpected issues

5) Will you need to make investments? Hardware? Designers? Calculate these figures.

6) Add a month (or 2) to the above, if your project fails to start making revenue, you'll need to find yourself a job - well, depending on how easy it is for you to find a good job...

It's an amount you need to calculate. Don't underestimate.

Then you're ready to roll.