it takes time to build a quilting business....unless you have lots of start up money to get you going/through for the first 3-5 years i would not expect to quit a good job & replace it with a just starting out quilting business...do you already have a customer base? have you been quilting for people? making money with your quilting?
i've had a business for 8 years now... i still work full time= in another field...the past 3 years i have made a profit with the quilting but i do not feel like i can pay all of my bills and maintain my current (life style) with just the quilting yet- maybe if we had retirement = or something else... I stay busy enough with it- i make plenty to 'support my quilting habit' and allow us the fun extra's- outside the monthly budget, like long weekends away, vacation fun, and some money in savings...i do not have to get into the household budget to enjoy my quilting, and i have a pretty good repeat customer base-adding a few new customers every year- if something happened to my job i might be able to spend more time at it & make more money- but it would be stressful - at some point maybe i will decide to retire & make it my primary income- but we need to be debt free before i even consider it.
of course if you plan to open a quilt shop thats a whole different story- you need money for your retail space, stock and the 'gumption' to work 18 hours a day...lots to think about- i would try to get started- while still working & see how that goes- it's seldom a good idea to leave a good job without a sure thing in the wings